Journal of the History of Biology, Vol. 1, No. 2

Illigerand the BiologicalSpecies Concept ERNST MAYR Museum of Comparative Zoology Harvard University, Cambridge, Massachusetts

The almost endless variety of species definitions and species concepts can be sorted reasonably well into three groups.' The first two were clearly articulated by the philosophers of scholasticism although the roots of these concepts are in part much older. This is particularly true for: (1) The essentialist species concept assumes that the diversity of nature, inanimate and organic, is the reflection of a limited number of universals which are fixed, unchanging, and separated by well-defined discontinuities from other universals. This concept ultimately goes back to Plato's concept of the eidos, and when later authors speak of the "essence" or "nature" of something they have the same concept in mind. The essentialist tradition is still surviving in the writings of a few authors raised in a Thomist tradition. One of the special aspects of the essentialist procedure is that ever since Aristotle there has been a close affinity between classifying into genera and species and the procedures of logic. This is particularly well demonstrated by Linnaeus, Cain pointed out (1958).* (2) The nominalist species concept is based on the rejection of universals by Occam and his followers. This species concept was maintained by Buffon in 1749 in the first volume of his Histoire Naturelle, by Robinet (1768), and by a few modem writers. A statement by Bessey (1908) expresses this viewpoint perfectly: "Nature produces individuals and nothing more. . . Species have no actual existence in nature. They are mental concepts and nothing more. . .Species have been invented in order that we may refer to great numbers of individuals collectively." (3) The biological species concept. This concept, in which 1. For a fuller discussion of these species concepts see chap. 2 in E. Mayr, Principles of Systematic Zoology (1968). *Sources cited in text and footnotes by author and date will be found in the Bibliography at the end of this paper.

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species are defined as "reproductively isolated natural populations," accepts species as realities of nature based on a relational property ("noninterbreeding") rather than on an intrinsic property (Mayr, 1957a, 1963). While the two scholastic species concepts are applicable to inanimate objects, the biological species concept is applicable only to organisms, indeed strictly speaking only to sexually reproducing organisms. Possession of a shared genetic program is the common tie uniting individuals derived from the gene pool of a given species. No two individuals of a sexual species are the same, and yet they share the same isolating mechanisms and through these are reproductively isolated from other species. This concept is so radically different from the essentialist and nominalist species concepts that it is of interest to ask how it originated. The Origin of the Biological Species Concept The history of the origin of the biological species concept has not yet been written. It is evident, however, that the concept emerged gradually. Numerous authors from 1749 to 1900 proposed species definitions that might be taken as versions of a genuine biological species definition provided one does not study their context too carefully. The prototype of such definitions is the celebrated one in volume 2 (page 10) of Buffon's Histoire naturelle (1749): We should regard two animals as belonging to the same species if, by means of copulation, they can perpetuate themselves and preserve the hkeness of the species; and we should regard them as belonging to different species if they are incapable of producing progeny by the same means . . . [continues to say that offspring of a crossing between two species would be sterilel. For we have assumed that, in order that a species might be constituted, there was necessary a continuin a ous, perpetual and unvarying reproduction-similar, word, to that of the other animals. Lovejoy (1959a, p. 94), in his perceptive analysis of Buffon's species concept and evolutionary thinking, comments quite rightly: "This language, it will be observed, implies not only that species are real entities, but also that they are constant and invariable entities." Did Buffon propose a biological species definition? We can ask this same question for all definitions of the ensuing one hundred years which refer to fertility of matings -for example, those of Kant, Oeder, Cuvier, Voigt, Oken, and so forth (Mayr 1957, Lovejoy 1959b). In order to be able to

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liger and the Biological Species Concept answer this question, it becomes necessary to analyze more closely the components of the biological species concept. Most historians of biology have looked at species definitions largely from the point of view of evolutionism. The question always asked is: Does the species definition indicate that the writer believed in evolution or does it indicate the opposite? Little interest is shown in the species definition per se. This is particularly well demonstrated in Lovejoy's discussions on the species concepts of Buffon and Kant (Lovejoy 1959a, b). The essentialist recognized membership in a species on the basis of similarity. This approach worked quite well when applied to inanimate objects, but it created all sorts of difficulties when applied to organisms, as is obvious when we look at the many attempts made to define species in the seventeenth and eighteenth centuries. How can we know whether or not two individuals share the same "essence"? This can be assumed as long as they are very similar-that is, as long as they "share the same characters," but what are we to do when individuals are as different as are males and females in sexually dimorphic animals, or as larvae and adults, or any of the many other strikingly different variants found in so many species? Variation was, from the beginning, the Achilles heel of the essentialist species concept. No nonarbitrary method is known by which one can determine what objects share the same "essence." In the case of inanimate objects, inference from similarity gave satisfactory results. But this criterion was totally inadequate in the case of sexual and age variation. The question thus arose: Is there any other criterion by which one can determine "shared essence"? To this a biological answer was soon forthcoming. The first author, known to me, who made use of this new criterion was John Ray (1686): In order that an inventory of plants may be begun and a classification of them correctly established, we must try to discover criteria of some sort for distinguishing what are called "species." After a long and considerable investigation, no surer criterion for determining species has occurred to me than the distinguishing features that perpetuate themselves in propagation from seed. Thus, no matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as to distinguish a species . . . Animals likewise that differ specifically preserve their distinct species permanently; one species never springs from the seed of another nor vice versa. 165

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The language used by Ray, as, for instance, his characterizadon of variations as "accidental," indicates his essentialist heritage; but there he found a splendid compromise between the pragmatic experience of the naturalist who can actually observe what belongs to a species, and the essentialist definition which demands an underlying shared essence. The entire range of amplitude of variation which any given pair of conspecific parents can produce in their own offspring was obviously contained within the potential of the essence of a single species. The real importance of reproduction for the species concept, then, is that it permits inferences on the amount of variation compatible within the realm of a single essence. The earliest "biological" species definitions thus were purely essentialist definitions in their philosophical conceptualizations, adjusted to the remarkable amplitude of variation found in biological species. In spite of a new superstructure of various biologically sounding new terms, there was no real departure from the conventional typological species concept. As long as the species was considered static and permanent, separated from all other species by a bridgeless gap-that is, as long as the essentialist and creationist dogma dominated the thinking of systematists and philosophers-emergence of a truly biological species concept was impossible. Population thinking as well as the acceptance of evolution had to be adopted before this could happen. We find numerous species definitions in the nearly two hundred years from Ray to Darwin which affirm on one hand the fixity, pernanence, and bridgeless discontinuity of species, and yet use biological criteria to reconcile the seemingly discordant evidence of conspecificity ("that which comes out of seeds of the same parent"). Buffon strengthened the boundaries by providing criteria for non-conspecificity: cross-sterility. Blood relationship now became the touchstone of conspecificity. The words "common descent" so frequently used by writers of this period had this purely operational meaning (of blood relationship) rather than a belief in evolution, as was later contended by some superficial historians. When such an emphatically antievolutionary author as von Baer (1828) defines the species as "the sum of the individuals that are united by common descent," it becomes evident that he does not refer to evolution. To the creationist it simply meant descent from the pair that had been originally created. Expressions like "community of origin" or "individus descendants des parents communs" (Cuvier) are frequent in the literature of that period. As Kant stated, "The artificial classification deals with classes, which are grouped together upon the basis of similarity, the natural classification 166

Miger and the Biological Species Concept deals with lines of descent, grouping animals according to blood kinship" (see Lovejoy, 1959b). Lovejoy demonstrates convincingly that the context of Kant's remark makes it fully evident that this sentence refers to descent within the species and does not indicate any conflict with Kant's essentialist philosophy. It is difficult to get a clear picture of the thinking of naturalists of that period. One reason is that, with a single exception, they fail to provide a thorough discussion of the species problem. Rather, they refer to it in a sentence here and in another sentence there. One has to piece their ideas painfully together from such little fragments. Lovejoy and others have done this as well as it can be done. The single exception is Johann Karl Wilhelm Illiger. He is the only one2 of all the naturalists of that period who has left an entire essay of more than a dozen pages on the species problem. Johann Carl Wilhelm Illiger was born on November 19, 1775, in Braunschweig. His father, a merchant, provided him with an excellent education and encouraged his hobby of studying and collecting birds and mammals. At the age of fifteen he came to the attention of the well-known entomologist, J. C. L. Hellwig, who asked him to help him in the arranging of his insect collections, and who finally invited him to become a member of his own household. Illiger's plan to study medicine was thwarted when he became ill of tuberculosis, a disease he had to fight the rest of his life, and to which he succumbed when only thirtyseven years old. The enforced leisure gave Illiger the opportunity to write his Terminologie when he was less than twenty-four. After completing his university studies at Helmstedt and Gbttingen, he founded an entomological journal, the excellence of which brought him an honorary doctor's degree from the University of Kiel in 1806. In 1810 Illiger was called by Wilhelm von Humboldt to the newly founded University of Berlin to be in 2. I make this statement in full awareness of chap. III of pt. 1 of Lamarck's Philosophie zoologique, entitled "Of species among living bodies, and the idea that we should attach to that word." The whole argument of Lamarck's discussion is that species do not really exist. A few quotes may demonstrate this: "These groupings [such as species and higher taxa] are altogether artificial . . . nothing of the kind is to be found in nature . . . nature has not really formed either classes, orders, families, genera or constant species but only individuals. . ." (pp. 20-21). It is the principle of plenitude which leads him, perhaps more than anything else, to deny the distinctness of species. "These species [of large general merge more or less into one another so that there is no means of stating the small differences that distinguish them" (p. 37). This absence of sharp distinctions between species is repeated again and again. (Page references are to the Elliot translation, Hafner Publishing Co., 1963, reprint of the original 1914 Macmillan edition).

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charge of the new University Museum. Only three years later, on May 10, 1813, he succumbed to his illness. What he achieved in these few years is almost without parallel in the history of taxonomy. This is not the place to report on his achievements, particularly since there is an excellent chapter on Ihiger in Stresemann's History of Ornithology.3 Instead, I will merely present a translation of his essay on the species. This is included in his Terminologie,4 an early biological dictionary. The essay on the species is interesting because it reflects so well the conflict between the essentialist dogma (still dominant in Central Europe) and the findings of the naturalists. Some of Illiger's statements show that he was clearly ahead of his time, others that he was still tradition-bound. As a consequence, the essay is a curious mixture of quite modem ideas and time-honored conventions derived from Aristotle, the scholastics, and Linnaeus. The essay follows the Foreword and is paged in Roman numerals which are inserted in the translation for ease of reference. I believe the following is the first translation of this essay into English. *

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Einige Gedanken uber die Begriffe: Art und Gattung in der Naturgeschichte [Thoughts on the concepts species and genus in natural history] Since a period of a whole year has passed since the completion of this work4 and its printing, I had an opportunity to do some further thinking about matters which occur in the introduction and in the section about the system, because they were too important, not always to be kept in mind during my cogitations. What is here said comprehensively about species, genus and related matters, is in part the more mature product of further thinking on the subject and may serve as correction and clarification of some of the statements in the body of this volume; in particular I hope thus to elicit the judgment of experts on these matters the influence of which on the treatment of the entire 3. E. Stresemann, Entwicklung der Ornithologie (Berlin: F. W. Peters, 1951) xv + 431 pp. For other biological literature on IlUger see E. Stresemann, J. Ornith., 70 (1922), 498-503; Botan. Museum Koenig (Bonn), 1 (1950), 43-51, 126-143; see also H. Lichtenstein, Abhandl. Deut. Akad. pp. 48-64. Berlin 1818 (1814-1815), 4. Johann Karl Wilhelm Illiger's Versuch einer Systematischen vollstandigen Terminologie fur das Thierreich und Pflanzenreich (Helmstadt: C. G. Fleckeisen, 1800), xlvi + 470 pp. The Foreword (pp. VII-XXIV) is dated July 1798; the Dedication to the Duke of Braunschweig, September 1799. The translated essay begins on p. XXV.

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Mllger and the Biological Species Concept natural [xxvi] history is so important that nothing is closer to my heart than to be thoroughly instructed about it. July 1799 It is necessary, first of all, to determine what the species is. It is the totality5 (Inbegriff) of all individuals which produce fertile young with each other. Nature herself seems to dictate this definition of the species. We can determine the species only on the basis of experiences about reproduction, and it is an error if one assumes, as is usually done, that the species originates through the extraction of common characters shared by several individuals.6 One has fallen into this error because one confused the species itself with the diagnostic characters of the species which the naturalist needs for his system, and because one thought that one had to apply the definitions of species and genus that are used in logic to organisms as well.7 However, the wrongness of this application is at once evident as soon as one considers that in logic varieties do not [xxvii] occur of which there are so many among organisms and to which the logical definition of the species applies equally well. For the logician calls a species any group of individuals which agree with each other in certain attributes. Black and white humans are for him species of his genus Man. Men and women are for him species of his generic concept Man. In natural history we cannot allow 5. Begriff, or Inbegriff, is difficult to translate. Totality is not quite right. I would prefer quintessence if it did not sound so much like the scholastic essence. Many taxonomists have spoken of the definition of a species (taxon), but using the word "definition" for a thing is not correct. Here, and in other places where it is difficult to find an exact equivalent of the German word in English, I have added in parenthesis the original German word in italics. 6. See G. G. Simpson, Principles of Animal Taxonomy (New York: 1961), p. 86, for a refutation of the "characters in common" approach in taxonomy. It is interesting to note that Illger fought this misconception in 1799. And yet, he upholds it in his discussion of the genus (See his footnote on pp. xxxvi). 7. Illiger saw this far more clearly than Linnaeus and other taxonomists of the eighteenth century. Their exclusive "definitions" of species, and their use of dichotomous keys as a method of classification indicated how strongly they tended to equate the method of classification with the method of logic. Although the empiricists from Adanson and Illiger on turned their back on a compliant application of the methods of logic to the procedure of taxonomy, it has been only in recent time that logicians have recognized that taxa are often characterized by overlapping characters. See Beckner, The Biological Way of Thought (1959), pp. 22-25, under the term polytypic. Since taxonomists traditionally have applied the term polytypic to taxa containing several taxa of the next lower categorical rank (e.g., a species with several subspecies), Sneath (1962) has proposed the term polythetic for Beckner's concept of polytypic.

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so much arbitrariness for the species or else there would be a continuous vacillation. Sex, variety, and species would be one and the same concept, to judge from the quoted examples, depending on the particular viewpoint adopted at that particular moment. This is quite unacceptable if we want to achieve a sound knowledge of organisms through natural history. Not only our needs, indeed a study of nature herself, has given and clearly determined, something that we cannot presume to be able to determine on the basis of arbitrarily chosen characters and viewpoints.8 Is it not a law of nature9 that animals of different species are not fertile with each other, or, if they reproduce, that the young which issue from such a cross [xxvIII] are sterile? Thousandfold observations have taught us this. We thus follow nature when we accept this as characteristic for the concept of the species which nature herself has given as the basic quality (Bedingung) of the species. I want to remove an apparent contradiction from this sentence before I continue. When we observe how most naturalists go about in the determination of species, we must concede that only few of them derive these determinations from observations about the stated law of nature [= sterility barrier] but rather that they decide about the species in their workrooms on the basis of certain diagnostic characters, and reduce to varieties what others have determined as species. Anyone who himself has described a number of species, being the first to have made them known, or who has critically examined species that had been described as new, has been in the same position. However, the naturalist acts in these cases entirely on the basis of analogy.10 He has abstracted from other previously known species what their essential or accidental characters are and has thus formulated for himself, distinctly or indistinctly, rightly or wrongly, the laws for that which characterizes species, and what can be considered only [xxix] as criterion of varieties. Thus, when he finds that a number of individual organisms differ from other known species in certain characters which in the case of other species are con8. Here Illiger rejects the nominalist thesis of the arbitrariness of species definitions. 9. In the fifty years since Buffon first clearly stated this, it has become a "law of nature." 10. This is one of the earliest if not the earliest discriminations between the species as a category and the species as a taxon. As Simpson has pointed out with particular clarity in Principles of Animal Taxonomy, the naturalist uses the characters presented by a taxon as evidence on which to base inferences concerning the categorical rank of the taxon. As Illiger says correctly, he acts in most of "these cases entirely on the basis of analogy."

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Iliger and the Biological Species Concept sidered as important and distinguishing, then he distinguishes them as a separate species. This separation, however, is to be considered as provisional, and only experience can decide whether the species is founded in nature or not. It would be quite wrong to declare the distinguishing characters to be the basic criterion of species, since the quintessence'1 of species consists only in the continuously fertile reproduction.'2 The remainder is only coincidental, and we cannot claim that it is fundamental for the species, as long as we cannot demonstrate invariable coexistence with that which indicates the species [fertile reproduction]. Nature continues to produce varieties, and only when she has exhausted all her germs13 is the extent of all the forms and properties given which a species is capable of producing (die bei einer Art stattfinden kbnnen). This is the reason why it is so difficult to distinguish the properties which characterize species from those of varieties. And yet we must discover them if our knowledge of organisms is not [xxx] to remain uncertain forever. We must try to enlarge our experience as greatly as possible; the greater the wealth of our observations the closer we will come to our goal. We will surely not object to let species lapse that were made in that manner when new knowledge convinces us that these species are after all only accidental deviations of other species, or when we see that the same difference which we had believed to have to consider as a species character turns out in similar species to be merely an aberration. To separate Lymexylon proboscideum as a distinct species from dermestoides was excusable because one considered the tufted palpi always associated with a very different coloration of the body as an essential species character. For at that time one had not yet observed 11. Illiger says "das Wesentliche der Art," which can be translated as "the gist of the species," "the heart of the species," or "the most important aspect of the species," avoiding the terms "essence" or "essential" with their scholastic connotation, which would be the most literal translations of Wesen and wesentlich. The context of Illiger's discussion shows clearly that the essentialist way of defining things and of looking for underlying universals has very much lost its hold on him, at least as far as the species definition is concerned. It is important, for instance, to notice that he bases his argument on observation of data rather than on "'logical proof." The same comments are applicable to Illiger's use of "wesentliche Kennzeichen" (basic characters), as for instance, on p. XXXII. 12. This is about as progressive a statement on the species as one finds for the next seventy-five years. It is only the context which shows Illiger's strong essentialist commitment. 13. One finds other contemporary references to the potential of species to vary and the definite limits of this variation, but I am unable to give the antecedents of this idea. Is it connected with the principle of plenitude?

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copulation in this genus nor did one know of an analogous example where the male differed from the female in a similar manner. However, as soon as Hellwig showed on the basis of repeated observations that proboscideum is only the male of dermestoides, no logical naturalist hesitated any longer to combine it with dermestoides [xxxi] in a single species, nor did he hesitate to add to his store of information a new item about sexual dimorphism among beetles, suitable to draw valuable inferences for other analogous cases.14 The illustrious Jacquin separated the monogynous hawthorn Crataegus monogyna from the ordinary hawthom Crataegus oxyacantha since it had only one rather than two pistils, and he considered this difference together with a correlated difference in the outline of the leaf to be sufficiently important to justify specific distinctness. However, as soon as someone demonstrates that the two types of plants can be produced from the same parental stock and that in the monogynous flowers the single pistil is not central, as is usual, but lateral, and that vestiges of the second pistil are not rare, and finally that the leaf shapes intergrade, then Jacquin will surely withdraw his species and combine it with oxyacantha as a variety. It is thus established with certainty that information about fertile reproduction is the only arbiter of the validity of species, that one can only with its help distinguish that in the form which is permanent from that which is [xxxii] accidental, and that all other judgments about the sameness or difference of species can only be considered as tentative and that their weight depends on their agreement with the fertility data. A primary function of natural history is thus to determine species correctly. For it is only in this way that we can learn the basic"1 characters which differentiate species from species, and species from varieties. Basic characters of a species are those which always and under all conditions remain attributes of the species. Since we have learned by experience that there is a large number of species, each species must have some peculiarity by which it differs from all others; otherwise there would be only a single species. This peculiarity is particularly well expressed in the way in which its organization is modified for the particular purposes of the species, which in each species are subject to its particular envi14. The unmasking of several species as different sexes or age stages of the same species was a frequent occurrence at that period and involved some of the most common species. In the mallard, for instance, Linnaeus described the female as Anas platyrhynchos and the male as Anas boschas, and in the goshawk the adult as A. palumbarius, and the immature as A. gentilis. No matter how different these "species" were, they were combined as soon as their "common descent" was established. Biological criteria invariably had primacy.

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Ihiger and the Biological Species Concept ronment (besonderen Verhdltnissen unterworfen ist). Reason as well as experience teaches us that each species reveals the differences embodied in its internal organization also through externally visible differences. It is inherent in the concept of an organized body that all of it is mutually interrelated by function and purpose [xxxu], that its parts thus have a fundamental connection with the whole, and that thus the functions as well as the structures related to these functions determine each other mutually. In this way we may hope to be able eventually to compile a logical register in which the important characters are separated from the unimportant ones, and on the basis of which we can decide what is a species and what a variety. The activity of those who increase the number of known species15 is thus of the greatest importance because this enlarges our field of observation and permits us to substantiate our generalizations. Equally praiseworthy are the observations of those who, by renewed investigations, either confirm previously discovered species or demonstrate which of these species are only varieties. For we can never have enough observations if we want to use them as bases for entirely reliable conclusions. In order to find the species characters we must look for them in the habitus. The habitus of a species is the totality of all characteristics that we can observe in all the individuals of the species taken together. The habitus is in a way the picture, painted by our mind [xxxIv], of the total impression of a species integrated from the impressions (Vorstellungen) of the individuals. There are two ways in which we can proceed in the description of a species. Either we can break up that picture, or the impression of the totality of the species, into its components and thus indicate the individual characters so that that which was previously clear now becomes distinctive (deutlich), or we can derive the characters from single individuals, compare them with other individuals of the same species, and then compose an entire whole from these individual components. It is in this manner that the concept of the species can be expressed in words. It is perfectly evident that one will encounter in this concept only general characters which are found in all individuals of the species. All deviations among the individuals subordinated under this concept relate either to a particular 15. It is rather amusing to notice that Illiger found it necessary, as early as 1799, to justify the importance of describing additional species. At that time, probably fewer than 25,000 species of animals were known, compared to the more than 1 million Recent species now known. But since the total number of living species is variously estimated to be 3, 5, or even 10 million, the task of describing them all appears each year more formidable to the contemporary systematists, and the justification for indiscriminately describing all of them increasingly questionable.

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individual only, or characterize a varietas if they are more important and are shared by several individuals. If one defines as essential only those characters of the species which are constant in the species, then one can define the variety as any deviation in the species in nonessential characters [xxxv]. Thus the habitus is that by which we know a species, and in it is contained that which distinguishes a species externally from other species. We can determine this only by a comparison of this habitus, and of its description with other descriptions. From such a comparison emerges the character of the species. Finding it is greatly facilitated by the genera, given to us by nature. For we find that certain species agree with each other in more features than with others which among themselves show similar agreements. By placing the similar species together and arranging them in clusters (Haufen), we are able-just as we were for the individuals of the species-to form a picture of that which the species of such a cluster have in common with each other. This picture is the habitus of the genus, and the same is true of it, with appropriate reservations, as what has been said above about the habitus of the species. The cluster (Haufen), or the quintessence of all those species, which share the characters of the habitus, is the genus. There are certain species which do not share such characters with species of any other genera [xxxvi], and each such species must be placed in a separate genus. The differences of the genera are determnined in the same way as those of the species. One can extract from the species that belong to a genus all that which is contained in the habitus of the genus. In view of the fact that the genus definition, which is nothing but the habitus of the genus expressed in words, will be found in its entirety in every species of the genus, it is obvious that one needs to mention of each species only that which is not contained in the generic description in order to describe that which is peculiar to the species. Those features of a species which differentiate it from all other congeneric species form the species diagnosis (Differentia specifica),16 which naturally remains changeable [xxxvii] as long as we do not know all the species of the genus and the entire extent of variability of every species.* The comprehension of the species of a genus is greatly 16. In this paragraph Illiger outlines what is often considered the main feature of the Linnaean method. *Illiger's note: From this follows that one must study every species of a genus if one wants to determine the quintessence (Begriff) of the genus. Since this is often impossible, one must at least examine several species for their major features. To derive the quintessence of a genus from the study of a single species (which has been done) is an invalid procedure

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Iliger and the Biological Species Concept facilitated by the families17 (Familiae), or the subdivisions, which one can make inside the genus on the basis of certain characters. Such families recommend themselves the more, the more important the characters are in which the species of such clusters agree and the greater the number of such characters is. Genera must be natural and we cannot determine by arbitrarily adopted criteria which species we should place together in genera. However, we cannot demonstrate (darthun) the naturalness of genera in the same way as [we demonstrate] the naturalness of species, even though Linnaeus attempted to do this. He adopted the hypothesis that the creator had created in the beginning only a single species of each natural group (Ordnung); that varieties had gradually originated through reproduction; that these had become the archetypes (Urbild) for the genera of these orders (Ordnungen); and that the species of a [xxxvmj genus had arisen from a common stem and that they were tied together through this tie of relationship.'8 We must, nevertheless, leave this as an unproven tenet-indeed as one that contradicts the nature of the species-until some day new observations will give us the key to the secrets of nature; how she creates species and how she converts accidentally arisen aberrations (Abaindrungen) caused by extrinsic effects, into hereditary varieties. In the meantime, we must take the facts as they now are. Since we find, indeed, in nature that several species agree very much with each other in their habitus and differ in this manner from others, and since we see that one species, owing to this greater agreement, shows closer affinity with a number of species than with any others, it is a natural conclusion to assume that nature herself had formed these aggregates. It is in the nature of our cognitive ability to combine this under a general concept in which it perceives a correspondence in several characters. It expresses this concept in a word and thus forms the genus. However, if the genus wants to claim naturalbecause one is apt to include in the generic diagnosis certain species characters which do not occur in the other species of the genus. 17. The category family, now designating a rank between genus and order, was not used by Linnaeus, but was beginning to be used in the last decade of the eighteenth century, particularly by French taxonomists. Illiger uses the term for a different rank, that is, for a subdivision of the genus. 18. This is about as close as Illiger ever comes to discussing evolution. What he really says is that related species look as if they had descended from a common ancestor, but that such an assumption is incompatible with the essentialist species concept. The essentialist species was the impregnable fortress of creationism. Darwin, most perceptively, selected this core problem of evolution as the title of his work ("On the Origin of Species").

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ness [xxxix] and certainty, then the agreement of the species among themselves must be greater and more comprehensive than with any of the species of another genus. In order to make genera kno*n, we select from the concept of the genus those attributes which we consider more constant than others on the basis of our experience and by analogy. Through a comparison of these attributes with the attributes of other genera emerge the generic characters. We assign the species to genera on the basis of their agreement with these generic characters.'9 Among the attributes which we perceive in natural objects, two major distinctions must be made: Some of them concern form and are subject to a definite geometric treatment. These are the extensive properties.20 The others are called "intensive properties," and we perceive them as simple and distinguishable only by degree. These are more subjective, and are perceived dfflerently according to the quality [XL] of the senses of each individual. With them objective general validity is not to be expected. Thus, colors, scents, and so on, are not perceived identically by everyone. It is, therefore, only proper that in the selection of characters one gives preference to the extensive properties over the intensive ones, and takes from them the chief characters; however, one cannot deny that the intensive ones should not be neglected since they are often very constant and conspicuous, and since in many cases, it is possible to infer from them extensive characters. No one is apt to doubt that in organisms the more important parts are more constant2l and that unimportant parts are subject to great variability. From this follows as a second rule for the determination of generic characters that they must be based preferentially on the more important parts. The importance of a part can be recognized partly from its greater or lesser relation to the foremost vital functions (Lebensverrichtungen),22 19. In these paragraphs there is an attempt at a theory of classification. Ilger shares with other pre-Darwinian taxonomists the great stress on "characters." Indeed, as Simpson implies, these early taxonomists tended to classify characters rather than organisms. This was perfectly logical under their essentialist premises. (See also footnote 6.) 20. Illiger here obviously refers to some school of philosophy and attempts to relate its teachings to the taxonomic method. 21. That the degree of constancy of a character is correlated with its taxonomic importance has been again and again affirmed by taxonomists up to the present time. For a further discussion of this principle see E. Mayr, Principles of Systematic Zoology, (1968) chap. 10. 22. Many of Illiger's contemporaries were preoccupied with the problem of finding methods for an a priori weighting of taxonomic characters. Cuvier and Lamarck, likewise, gave highest weight to the physiological

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Mlligerand the Biological Species Concept such as nutrition and reproduction, partly from its close connection with [XLI] the nervous system, as with the sense organs, partly from the connection of a part with a very special purpose of the animal or the plant, and partly from the wide occurrence (Allgemeinheit) of a part which lets us infer its indispensability. And to turn around the statement made above, the importance of a character can be determined in part on the basis of experience, which calls our attention to parts through their constancy and through the invariable correlation (Zusammensein) of a part of a particular structure (Beschaffenheit) with others known to be important for the reasons mentioned above. For this reason the legs and the fins are surely of special importance among animals. Indeed, one ought also to include among the generic and species characters the intemal organs since they are the most intimate (ndichsten) organs. [The next five and a half pages are devoted to a rather scholastic discussion of the formation of natural and of artificial genera. This discussion seems rather meaningless to the modern reader.] [XLVI] In the same way in which we form genera from species, we form orders and classes from genera. The higher we ascend, the more general and simpler the characters are; and with the kingdoms, as the highest subdivisions of organisms, we reach the simplest and highest laws of organization. Naturalness must be the basic principle even in these divisions. Bibliography Baer, K. E., von. 1828. Entwickelungs-Geschichte der Thiere. Konigsberg. Bessey, C. E. 1908. "The Taxonomic Aspect of the Species," Am. Naturalist, 42, 218-224. Buffon, G. L. Leclerq de. 1749. Histoire naturelle, vols. I and II. Cain, A. J. 1958. "Logic and Memory in Linnaeus' System of Taxonomy," PrOC. Linn. Soc. London, 169, 144-163. Glass, B., 0. Temkin, and W. L. Straus, Jr. 1959. Forerunners of Darwin: 1745-1859. Baltimore, Md.: Johns Hopkins Press, 471 pp. Glass, B. 1959. "The Germination of the Idea of Biological Species," in Glass, et al., 1959, pp. 30-48. Lovejoy, A. 0. 1959a. "Buffon and the Problem of Species," in Glass, et al., 1959, pp. 84-113. importance of an organ. Yet interestingly enough, IlUger pays only lip service to these aprioristic principles. He sides with the empiricists and stresses the importance "of experience which calls our attention to parts that by their constancy and by the invariable correlation of a part of a particular structure with others" call our attention to their taxonomic importance. Invariant correlation, which plays such an important role in Darwin's taxonomic theory, and in the theory of classification right up to the present time, was duly appreciated by Illiger.

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ERNST MAYR 1959b. "Kant and Evolution," in Glass, et al., 1959, pp. 173-206. Mayr, E., ed. 1957a. The Species Problem. Publ. no. 50 of AAAS. 395 pp. 1957b. "Species Concepts and Definitions," in Mayr, 1957a, pp. 1-22. 1963. Animal Species and Evolution. Cambridge, Mass.: Harvard University Press. 797 pp. Ray, J. 1686. Historia Plantarum. Sneath, P. H. A. 1962. "The Construction of Taxonomic Groups," Symposia Soc. Gen. Microbiol. Cambridge (Eng.) University Press, no. 12, pp. 289-332. Zirkle, C. 1959. "Species before Darwin," Proc. Am. Phil. Soc., 103 (5), 636-644.

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Agassiz,Mendel,and Heredity* J. A. WEIR Hall Laboratory of Mammalian Genetics Department of Zoology, The University of Kansas, Lawrence

In dealing with the history of a subject, the value of each successive contribution should be estimated in the light of the knowledge at the period, not of that at the present time. -Louis Agassiz, 1867 (B. G. Wilder, The Harvard Graduates' Magazine, June 1907)

In the library of the Museum of Comparative Zoology at Harvard University, with its vast array of materials pertaining to natural history, there is a section devoted to agriculture. Now neglected and considered of little interest, it formed a significant part of the collection during the lifetime of the museum's founder, Louis Agassiz (1807-1873). It seems doubtful that any of Agassiz' biographers ever felt constrained to work over such seemingly irrelevant materials, although this would have revealed that the genial zoologist commanded a respectable fund of knowledge about practical agriculture. It is true that Agassiz sought, and obtained, generous support for the Museum (MCZ) and that he aired his views in opposition to Darwin before agricultural audiences.' But these are not points at issue. As contemporaries, Louis Agassiz and Gregor Johann Mendel (1822-1884) were no doubt exposed to some *This paper was prepared at Harvard University as a part of a project in the history of science supported by a Public Health Service Fellowship (1-F3-GM-32, 076-01) from the National Institute of General Medical Sciences. 1. Edward Lurie, Louis Agassiz; A Life in Science (Chicago: The University of Chicago Press, 1960), p. 387, referring to a reprint of Agassiz' last lecture, states: "On December 2, Agassiz delivered a lecture xn Fitchburg, Massachusetts, to an appreciative assemblage of farmers, animal breeders, and state legislators, hoping thereby to gain more funds for the museum by impressing rural folk with the significant information to be gleaned from the study of domesticated animals." Actually, over the years, Agassiz spoke frequently to agricultural audiences and was more interested in agriculture than was Asa Gray.

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of the same folklore, the same popular literature, and similar questions about the nature of heredity. Agassiz' remarks, made before prominent agriculturistsof the day, should throw some light on the state of the breeder'sart during Mendel'sformative years. Before quoting from reports of the MassachusettsBoard of Agriculture, I shall indicate why it has become difficult to reconstructthe historyof genetics. I Natural history achieved professional standing during the nineteenth century, at a time when colleges of liberal arts in the United States were responding to the claims of science. Meanwhile, chemistry's most ardent advocate, Justus von Liebig (1803-1873), had directed the attention of enlightened agriculturists and animal physiologists to the promises of chemistry while Louis Pasteur (1822-1895), himself a chemist, had provided medicine with revolutionary new methods. In the end the naturalists consolidated their position through the estab-

lishment of university museums and by claiming Darwin as their own. Chemistryfound support but little initial success in the newly formed agricultural schools, and medicine, already the sponsor of animal physiology (the most experimental of the biological disciplines), added bacteriology. Establishment of separate physical plants (often at great distances from one another), separate graduate programs, and separate libraries, while mitigating tensions and providing for rapid progress, served to cut off continuing opportunitiesfor fruitful contacts between the biologicaland physical sciences. For reasons of propinquity,historians of science have tended to concentrate on natural history and medicine. Perhaps these have been wise choices-providing perspective and permitting separation of the ephemeral from the eternal, the sensitive from the innocuous, and the frivolous from the profound. If we deal with a discipline as recent (dating from 1900) and as unfettered (only rarely with separate departmental status) as genetics, the obstacles become formidable. For the most part, it is the survivors of the second generation of geneticists, the first generation to be trained as geneticists, who now speak and write on the history of genetics. Based on personal recollections and a profoundunderstandingof the literature,current essays have a bland and mellow quality that is in sharp contrast to the contentious writings of the pioneers-men who reacted vehemently to the indifference, ridicule, and fierce opposition from the older disciplines. Only the remarkableT. H. Morgan (1866-1945), along with his inexpensive, inoffensive, 180

Agassiz, Mendel, and Heredity and economically useless Drosophila melanogaster, had immunity from direct assault. Final acceptance of genetics by the naturalists was grudging, and even then they admitted only the importance of the subject as an adjunct to Darwin's contributions.2 If we were to search out a contemporary of Mendel with the object of understanding the thought of Mendel's time and why Mendel designed his experiments the way he did, what would be the qualifications? Our candidate should be innocent of theoretical bias (this would rule out Darwin, whose use of anecdotes was tailored to an already formed point of view); he would need to be a keen observer, capable of putting his thoughts into clear prose, and, more than likely, he would turn out to be a zoologist because, although plants may be better suited to demonstrate the way heredity works, animals are better for revealing the phenomena in a general way. Louis Agassiz fits the description. II Louis Agassiz was not raised on a farm, like Mendel, so did not grow up, so to speak, with the domestic animals and cultivated plants of the farm. Nor was he born to wealth, like Darwin (it was the son, Alexander, who became wealthy and provided timely support for the museum). Agassiz was modest in his claims, and knowledgeable in a number of areas relating to agriculture. He was one of the three members of the State Board of Agriculture of Massachusetts appointed by the govemor and council. During his term of office, running from 1864 until his death, Louis served with alacrity and effectiveness. From the unpublished minutes of the Board we find that he was polite, a good listener, and constructive. Louis Agassiz was not an especially complicated person. Successes, failures (there were a few), power, charm-all were derived in large part from the one source, his boundless enthusiasm. The enthusiasm, in turn, was propelled by an almost inexhaustible store of energy. His career was one of contradictions and contrasts. He was always known as a student of Cuvier (1769-1832), but Cuvier died within a few months of Agassiz' arrival in Paris. Agassiz is known from his European period for his advocacy of a widespread Pleistocene Ice Age, 2. See, for example, Everett Mendelsohn, "The Biological Sciences in the Nineteenth Century: Some Problems and Sources," History of Science, 3 (1964), 39-59. "It is equally clear [of problems of nineteenth-century evolutionary thought] that the explanation for the long neglect of Mendel's discoveries lies in an understanding of the attempts to develop a theory of heredity to accompany the action of natural selection" (p. 52).

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but he got the idea first from Charpentier. Agassiz became best known in the United States for his teaching but, as with all men who throw most of their energies into teaching, he became less of a student and consequently something less of a teacher. He advocated widespread public support for science but many of his own endeavors were in areas of science that appeal strongly to the amateur. He was known for his capacity for generalization, but evolution, the great generalization to come out of natural history, passed him by. He evoked great and lasting acclaim from students of the humanities (by making it possible for them to share some of the joys of science without the rigors), but his name is not once mentioned by the present Agassiz Professor George Gaylord Simpson in his book The Meaning of Evolution. Few men have come as close as Agassiz to completely dominating a great institution, and yet the botanist Asa Gray (1810-1888), also at Harvard, lived to see his own quiet influence transcend that of the irrepressible Agassiz. Agassiz' views on inheritance, presented before the public meeting of the Board at Greenfield on December 15, 1864, opened as follows: Prof. Agassiz.-I had some thought of taking up for the subject of my lecture this evening, the physiological principles of breeding, with reference to what may be done to improve our various kinds of domestic animals; but as I see that these lectures are attended by ladies as well as by gentlemen, I may, perhaps, take this opportunity to make a few remarks upon this subject, which are akin to the present subject of discussion.3 Thus it turned out that Agassiz' seemingly offhand observations, presented at the morning session on cattle husbandry, are not to be found by reference to the Synoptic and Analytical Index, 1837-1892, whereas his evening lecture "Origin of Agricultural Soils" is listed. (The index includes references to reports published before the State Board of Agriculture was organized in 1852). Even though the printed Reports of the Board were increased over the years from three thousand copies to five thousand, then to eight, ten, and afterwards to twelve thousand and were widely distributed, a complete set is difficult to find today. Agassiz' last lecture is quite well known; it is in the MCZ library as a reprint, but there is still cause for confusion. L. C. Dunn writes: 3. Agriculture in Massachusetts, 1864. (Twelfth Secretary, Charles L. Flint, 1865), p. 127.

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Annual Report of the

Agassiz, Mendel, and Heredity Just two weeks before his death on December 14, 1873, Agassiz had delivered a lecture on "The structure and growth of domesticated animals." It was printed in the Naturalist (7:641-657). Although it carried a footnote, "delivered before the State Board of Agriculture at Barre (Massachusetts) December 3, 1872," Lurie (1960, p. 419) gives the date as December 2, 1873.4 Actually, two lectures with the same title were given in successive years; the second was a continuation on the same topic. The American Naturalist paper was a reprint of Agassiz' 1872 talk but omits the final paragraph, the one that puts in "a good word for the institution with which I am connected . . ." The first part of Agassiz' talk of 1864 related to size in cattle: the relation of size to geology, the advantages of small cattle under certain circumstances, the advisability of supplying lime when it is not naturally present. The audience, accustomed to Agassiz' authoritative pronouncements, was not to be disappointed: I have no doubt, from the interesting remarks I have heard yesterday and to-day, and the large amount of information I have been able to collect from the lips of so many practical farmers, that, having these suggestions, they will at once know how to apply them. I do not know how to do it. I have never been interested in raising a single cow, so I do not know how to take care of cattle, and would not know what to advise; but I am a physiologist, and know what are the principles of physiology, and I am satisfied that to raise large cattle, you must introduce into their systems, with their food, a sufficient amount of limestone to build up a large, bony frame, and that you must do this artificially, where nature does not provide the cattle with a sufficient amount of lime in the waters from which they drink, and in the rocks against which they rub themselves, to make their bones. With us, in the Jura, or in the canton Freiburg, in the Alps, which is a limestone country, every pail of water contains a large quantity of lime in solution, and every cow that drinks, drinks in bones, or at least lime, with which to make bones. That lime we must supply.5 The Alps still cast their spell over Louis Agassiz after twenty years in the New World. Having drawn attention to the importance of environment, the lecturer continued: 4. L. C. Dunn, "The American Naturalist in American Biology," American Naturalist, 100 (1966), 481-492. See footnote 1. 5. Agriculture in Massachusetts, 1864, pp. 128-129.

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Now, with reference to breeding. And here breedingcomes in for a share in making these good kinds or poor kinds of cattle. Let us examine what the native animal is;-and again I say, that when you have these principles before you, I know that, in a very short time, whatever value they have will be applied to the promotion of agricultural improvement. I believe that all our discussions are a little too loose; that we don't understand all the elements of the question sufficientlyto know by numerical value what there is in one and what there is in the other propositionthat is discussed. I hear the characteristics of a dairy cow spoken of in contrast with those of a beef animal; but I want to know what there is that makes up two such different animals. Differences in form have been alluded to, and differences in situation have been alluded to also, and these ought to be considered separately; but there are differences in substance of which I have heard nothing said. I should like to ascertain-and for that experiments must be made which we have not on hand-what is the percentage of bone in the best animal to fatten or to raise for beef, what the percentage of skin, of horn, of hoof, of blood, of lymph, of liver, which goes to make up the sum total of the weight of the animal, and how far there is a difference in those respects between the differentkinds of cattle which we raise.6 This proved to be a false start, a digression, which was a favorite ploy of Agassiz) leading up to a good word (153 words by actual count) for the Museum of ComparativeZoology in Cambridge. Back on the track once more, the professor continued: Now, with reference to breeding. In breeding, we must remember that every animal has a number of elements in it by which it may be distinguishedfrom every other animal. All the individuals belonging to one kind of cattle, all cows and bulls put together, with their calves, or the whole race of cattle, for instance, have certain properties which distinguish them from the horse, the donkey, the sheep. Now, the primary peculiarity of all animals is that they transmit, generation after generation, that sum total of qualities. Inheritance or transmission of qualities is the primary feature of all animals; and this transmission consists not only in transferring, generation after generation, the general qualities of the whole race, but in a differencewhich is fundamental. There is always a certain porportionof male and female. 6. Ibid, p. 129.

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Agassiz, Mendel, and Heredity Whatever be the qualifications or the peculiarities of the kind of animal, there is that primary difference at once established; there are so many males and so many females of each kind born, by which the process of reproduction is maintained. That is one of the primary laws of organization, and that essential difference extends throughout the whole animal kingdom and throughout the whole vegetable kingdom. There is that essential, primary difference between one set of individuals and another set,-that one certain ratio is male and the other is female; and these two elements combined constitute the means of the transmission of those qualities which are common to them all as a whole. You must, therefore, always take these two elements into consideration in the propagation of animals,-the qualities of the two sexes. Now, individual animals, again, have some very important share in this. If I look at this assembly, I see no two individuals alike, and if I go out of doors, the same impression continues. I see no two men nor two women alike; and if I go to the farm, I see no two heads of cattle alike. Besides these common features which go to make up humanity, or which go to make up the cow world, the horse world, the donkey world, the sheep world, the pig world-besides these common features, there is individuality noticeable everywhere, and that individuality is marked. Every shepherd knows how to distinguish every individual of the flock he owns. Now, this individuality is not altogether transmissible, as the general properties which go to make up the whole race are; only a part of these peculiarities of the individual being are transmitted, generation after generation; for you will notice that the children of one family are not all like the father, nor are they all like the mother, nor are they all even a mixture of the two. And what is true of man is true of animals. Every individual born from the same parents may differ from both parents, or may have a certain degree of resemblance to both parents. Let us, therefore, not forget this second law of reproduction, which consists in a partial transmission of individual characteristics, while there is a total transmission of those general features which go to make up the kind of animal. We never expect to have a horse born from a cow-we expect a calf, a young cow or a young bull; and we expect that, within a certain limit, that calf will share the properties of either the mother or the father, but we know that it will not do this fully. Now, what can

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we do to ascertain what we shall get? -for it is on the assumption that, having a male of certain qualities and a female of certain qualities, we can get the best animal out of the two, that we proceed in introducing a certain distinct animal into a herd, with the expectation of improving the progeny of that herd. We may make tremendous mistakes in so doing, and I want to point out the basis of these mistakes, because they are the foundation of all our disappointments. I am not prepared to tell you how to remedy all these disappointments, but I will point out their sources that you may, in your practical wisdom, devise the means to obviate them. An individual, however distinguished he may be in himself, has, in consequence of this law of inheritance, combined in himself a variety of elements which may reappear in his progeny. Now, remember that an animal may be as distinguished an individual as you could wish to have as the head of a desirable progeny on your farm, and yet, notwithstanding these apparently eminent qualifications, he may be vitiated for the purpose for which you want him because of some characteristics of his ancestors. An animal is not made up of the elements of his father and mother alone; he has also the elements of his grandfather and of his grandmother, and he has the elements of his whole race behind. Now, within certain limits, these ancestral elements come up again, and they come up again especially in the third generation. There is a singular law which pervades male animated nature throughout, which is recognized as a physiological principle, and that is, that some features of an aniimal are transmitted, not so much directly to his immediate descendants, but to his grandchildren, to the third generation. You must, therefore, before you can be sure of proceeding in the right way, know the ancestry of your breeding animals for at least three generations back; otherwise you may have cropping out the characteristics of the grandfather or grandmother where you least expected them; and the grandfather or grandmother of that distinguished individual may be the last animal you would want to have on your farm. Do not, then, trust animals that are trumpeted all over the country as distinguished animals, before you know what were their grandparents, otherwise you may be greatly disappointed and deceived. That is the first condition of successful breeding. You must know that you have a family which has ancestral qualities to be depended upon before you introduce that animal as an element of growth into your herd. I am

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Agassiz, Mendel, and Heredity glad that I do not know any of the valuable and celebrated animals in the community, because I am able to speak with a degree of independence which I should not possess if I knew my friend A, B, or C had a valuable bull, or a valuable horse, which yielded him so much income, and whose reputation it was desirable should be kept up. I have no such friends, I am happy to say here, and, therefore, I can speak upon principles, and shield you, by those principles, from the mischief you might do by trusting too indiscriminately to representations which may be, after all, very indifferently founded. I think that the criterion of success will be the progeny of successive generations. I would trust such animals as have descendants, and as show a fine family in several generations, and out of such a family I would select my individuals for further propagation. Now, this matter of the partial transmission of qualities consists of other elements besides this male element,-there is the female-and there are other elments besides those of ancestral inheritance, which are to be considered. There are the qualities of herd, there are the qualities of species, there are the qualities of race. And here we must again inquire into two very different subjects. The qualities of breed and the qualities of species are totally distinct, and I think that the proper distinction is not always made. My friend, who spoke so learnedly, so fully, and with such an amount of experience, yesterday, on the culture of the grape, made, in one of his statements a mistake (if I am not mistaken myself,) in that very particular, when he used an expression which should apply only in one given sense and not in an indiscriminate one. A hybrid is only the offspring between two different species. A hybrid can never be produced between two varieties of the same species. Mr. Bull.-I used the common horticultural term. Prof. Agassiz.-I know, sir; but let us be careful to introduce into our discussions only such definite language as makes misapprehension impossible; for we want to have that precision which shall be beyond the possibility of cavil from misapprehension, and beyond the possibility of misinterpretation from looseness of statement. How shall we secure this with reference to these different kinds of animals? By using just such terms as will designate the one we want to designate, and that only. Now, species are formed in nature, with all qualifications; they are God's creations. Breeds are formed under the fostering care of man, and differ according to the circumstances under which they have been raised,

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-they are human manufactures. That is the difference between a breed and a species. All our cattle are of one species, and they produce nothing but cattle; and every species produces nothing but its own kind. Breeds are the result of the interference of man with these creations of God, in the manner which will suit his peculiar pursuits or objects, and they are his work. Men have made breeds. They are not God's creation, they are man's production; while species man never made. We have found them in nature; we have subdued them, we have appropriated them to our purposes; they have been endowed with certain peculiarities which are pliable, and they are capable of being impressed in various ways by man-one species more than another so that different breeds, more or less different, can be obtained. Among dogs, which are more pliable, physically, than any other of the domesticated animals, the breeds have a range which is astonishing. Compare a bulldog with a greyhound, an extraora King Charles' spaniel with a mastiff,-what dinary differencel There is no such difference among cattle or horses. And why? Because by nature this species was more pliable to influences than others. Now man has to apply himself to that pliability, and impress upon these animals those peculiarities which are useful or desirable for him. Now, these specific differences and these breed differences are of a different kind. A species transmits its characteristics unmistakably and always, and the sum total of its specific character is transmitted. A breed, being the product of man, transmits its peculiarities, its qualifications, only partially, and only as long as those things which produce them or maintain them are at work. Cease to take care of these animals in the way in which the differences produced may be maintained, and the breed itself runs out. You cannot perpetuate them without taking at least care that those conditions which will maintain the breed differences as they have been produced, are continued. Now, when you propagate animals, there is a certain limitation to the fecundity. Only individuals of the same species are absolutely fertile with one another. Individuals of one species with individuals of another species have only a limited fertility. You may be sure to see individuals of the same kind bring forth individuals of that kind and no other; and these individuals, you may be sure, will be capable of reproducing their kind in turn, generation after generation. But

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Agassiz, Mendel, and Heredity cross individuals of two different species with one another, and you at once obtain hybrid; that is, what we call hybrids, or what we call mules; and these hybrids or mules always propagate individuals of two different kinds, and their fecundity is limited; sometimes so extremely limited that even the first generation is sterile; sometimes partially fertile by a return to the parent stock. Between themselves, the individuals born from two different species are hardly ever fertile ad infinitum. I will quote an example to show what I mean more distinctly. The horse is one species, the ass is another species. Horse with horse produces horse, ad infinitum; ass with ass produces ass, ad infinitum. But horse with ass produces a mule, or a hybrid. Now, that hybrid always has part of the character of one parent and part of the character of the other parent. It is not a representative of any species, but it is a half-breed. And here the English names designate truly the characteristic of that animal. It is a "half-breed," or a "hybrid," or a "mule." Those three names apply to that kind of animal, and they should never be used to designate any other. The word "hybrid," the word "mule," and the word "half-breed," should never be used except to designate the progeny between two different species. And that progeny will differ according to the character of the father or the mother. The offspring of the male horse with the female ass is not the same as the offspring of the male ass and the female horse, by any means. What is commonly called a mule is the offspring of the jack with the mare. We do not raise the offspring of the horse with the ass; but in France they are sometimes raised, and are known there as bardots. Now, the bardot is a very different animal from our mule; it has a greater resemblance to a horse, only it is a small-sized donkey. The form of the head, the hoof, and the tail are those of the horse. Now, the reverse is the case with our mule, which has the size of the mare; but the form of the head, tail, and hoof, of the donkey. May we not, by these crosses, ascertain, in a measure, what kind of character the male will transmit to his progeny, and what kind of character the female will transmit to her progeny? I suppose that a thorough analysis of the difference which exists between the bardot and the mule, as compared with the horse and the ass, would give us a large number of very valuable hints as to what we may expect in the transmission of the qualities of the male and of the female to the progeny; for we have not yet made the experiments in breeding that will enable us to ascertain that with any

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degree of certainty, because, in all the experunents of which I have been able to find any record, the breeding individuals have been taken as if they had no ancestry-as if no qualifications could be transmitted to the progeny besides those of the mother and of the father. And yet, if we look to this law of ancestral transmission,we know that any progenymay show characteristics which are neither those of the mother nor of the father, but those of a remote ancestor, three generationsback.7 Remembering that Agassiz was describing the state of the art of animal breeding as it then existed (and as it is still practiced), what is the special significance of his words? There is a clarity and a logical manner of presentationthat go beyond the usual folklore. However, at this point I must introduce a digression of my own since it has some bearing on the credibility of the witness. At the meeting held the following year (1865) Agassiz again expounded at length, ostensibly on the spur of the moment, on the importance of making a clear distinction between species on the one hand and varieties and breeds on the other. In his scathing attack on the doctrine of evolutionhe made the statement: But if you tell us that you develop only such properties as are inherent in the plant, as are inherent in the nature of the animal, and that you add nothing essentially new, then that doctrine [transmutation of species] is at once repudiated. [Andlater] I do not suppose that by any particularwitchcraft agriculture is to do in the next five years very materially differentthings from what it has done before.8 After the audience had been dismissed (I am still speaking of the 1865 meeting) Professor Agassiz, by request, made a few remarks to members of the Board on the topic he had eschewed earlier, again because of the presence of ladies. He decried promiscuity, the system of harems in which "every male is made to be nothing but a breeding machine."He talked about the effect of the first contact between the sexes, stating: .l. .

a female which has been badly connected will never pro-

duce as fine a breed as one which was well mated at the first start; so that the ideas of the English aristocracy ought to prevailhere in orderto producethe best results." Finally, he commented on the high incidence of monstrosi7. Ibid., pp. 130-136. 8. Agriculture in Massachusetts, 1865 (Thirteenth Annual Report of the Secretary, Charles L. Flint, 1866), p. 73.

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Agassiz, Mendel, and Heredity ties in dogs in an early embryonic condition, calling for experiments and implying the reality of matermal impressions. Agassiz, like Darwin, seemed to subscribe fully to nearly all of the foLklore of the breeder and thus he proves to be an interesting witness. Other members of the Board had views in a number of areas that were far more in keeping with presentday knowledge. Returning to the 1864 address, Agassiz' emphasis on importance of pedigree and performance, the suggestion that appearances are outward manifestations of underlying transmissible elements (phenotype and genotype in modern terms), and the clear distinction between the properties of varieties on the one hand and species on the other were derived from many careful observations. Having described the situation, Agassiz the teacher (and this was characteristic of the man) suggested experinents that others might perform. This is not the way research gets done but, if someone well versed in practical affairs, well trained in quantitative methods, well situated with respect to time and space had taken up the suggestions, what might he have discovered? Agassiz' protocol for research was as follows: Now, therefore, we must begin our experiments with reference to the transmission of qualifications from the male or the female, if we would have at all a trustworthy basis. And how shall we proceed? Here I propose one problem for solution. I have no results to give, gentlemen, and you will at once see how difficult it will be to obtain a result at all; what extraordinary, costly and difficult conditions must be met in order to obtain a result that shall have any value whatever. But I think the time has come when we must stop arguing on a loose basis, when we must begin to make experiments that shall have all that scientific accuracy on which we can rely. I am sure that Massachusetts farmers are the men to do this work for the progress of agriculture, for I see from their discussions that whatever they do, they do thoroughly; that whatever operations they enter into they analyze to their satisfaction. Now, if they would ascertain what are the laws of inheritance, or in reference to breeding, let them first secure individuals from which they have eliminated the elements of ancestral transmission. That is the first thing to do; just as when astronomers compute their observations; they begin by looking over the observations, in order to know which they are to take into account, and which not. There are observations made by unskilful hands, and if

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they were taken into consideration,in a computationin which a thousandth part of a minute is an element of great importance, you see at once that a single incorrect observation would vitiate all the results of the good ones. Now, the first thing an astronomerdoes when he goes to work on his observations, is, to see how the observations were made, and on looking over the books, he sees at once that here are observationsthat he must leave out, page after page; and here are observations that look as if they had been made with the proper care, and these he will take as the basis of his computation. Now, you must proceed in the same way, and when you read of satisfactory results obtained by some experiment, you must not shrink from the painful investigation as to whether it was made with proper care, and a due consideration of all the elements which should enter into the computation. Therefore, tell your friends, and tell yourselves, when you are satisfied that they and you have made mistakes, that these previous observations are good for nothing, and go to work. Learn to tell yourselves that what you have done is worth nothing, and then you will be on the road of progress. It is difficult, but it is the advantage the scientific man has over the practical man. The training of scientific men consists in nothing else but in learing how to set aside their own doings, to criticize their own observations,so that they shall know what is worth listening to and what not. That is the source of our strength, that is the foundation of our value in community-that we learn (and that is our special office,) how to criticize whatever we do. Now, I think, from what I see here, that you will learn that very soon, and when you have learned that, you will proceed with confidence. The first thing to eliminate in this experiment concerning the transmissibility of the qualifications of any animal is the ancestralelement. How will you do that? By breeding one or two generations in-and-in, without affinity. Here I state a limitation which is not perhapsunderstood,and I will explain. In orderto have stock on which you can make a sound experiment,you must breed together individuals as closely allied as possible, but which shall have no family ties. There is one important element when you speak of breeding in-and-in. I have never heard the distinction referred to that I now make. Breeding in-and-in may mean, according to the way in which I hear it discussed,breedingbrotherand sister, or father and mother, as well as breeding together individuals which resemble one

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Agassiz, Mendel,and Heredity another very closely. Now, there is a vast difference between these two modes of breeding in-and-in. Breed Anglo-Saxon with Anglo-Saxon, does not mean that brother and sister should intermarry. The breed of Anglo-Saxon is improved by the intermarriageof Anglo-Saxons, but of Anglo-Saxons who have no family ties; but the breed will be spoiled if you breed in-and-in Anglo-Saxons, brother and sister, or mother and father. One is a moral crime; the other is the foundation of national superiority.You see at once the difference. Now do the same thing on your farm. Breed in-and-in, but do not permit incest among your animals. Breed inand-in those who are of the same kind, but do not breed in-and-in those which have such close family ties that you would breed disease in them by the closeness of the blood. That distinction is the first fundamental distinction of all good breeding. You must breed in-and-in, to have the proper stock to experiment upon, for several generations, so that you shall have aniimals that will hold the same ancestral relation to one another. You see, therefore, that to procure a proper animal for experiment will take you several generations. You cannot get that easily with cows; you may get it more easily with sheep; and in a series of experiments which I have proposedto some of my friends, I have advised them to take sheep, in order sooner to have the elements upon which to make sound and valuableexperiments. Now, when you have the third and fourth generation obtained in that way, by the connection of individuals closely allied to one another, but which have no blood relation to each other, then you have individuals from which you have eliminated the ancestral element that might re-appear in the next generation. Suppose you prepare in this way a number of coarse-wool sheep, so that you have male and female individuals which have no blood left except that of their own, and you prepare in the same way another number of merino individuals. Now, you cross them both ways -merino ram with coarse-woolewe, and, vice versa, coarsewool ram with merino ewe, and you will very soon ascertain what is the transmission of one male with one kind of female, and of another male with another kind of female. You will then have experiments which will begin to be valuable with reference to the law of transmission of the peculiarities of breed through breed; of that crossing between breed and breed which is so different from the intercrossing of individuals of two different species. The law of the transmission of qualities from breed to breed, in crossings of

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breeds, is yet to be ascertained. We have nothing but guesswork about it so far.9 Any student of elementary genetics will recognize here the design of his first experiment: two vigorous interfertile "stocks" differing in a number of characteristics, inbred to a degree, crossed reciprocally. We know now that Merino x Leicester (for example) would not have been a good cross, but the idea that materials should be chosen with regard to time and expense was a good one. Swine would serve better, and mice better still. Furthermore, with a rapidly maturing polytocous species, such as mice, the young produced from the cross (we can avoid calling them hybrids by designating them as the Fj), if merely left to their own devices, would produce another generation, the F2TMight not the reappearance of certain characteristics of the grandparents in different litters, or successive litters from the same parents, arouse extreme curiosity and whet an investigator's appetite for further experiments, further results, all possible kinds of matings, careful recording of pedigrees, and finally, discovery of the underlying principles? It is doubtful that Agassiz seriously expected anyone present to attempt the investigations that he outlined. In only a matter of hours he would address them again, this time on the origin of agricultural soils. Once again the distinguished members of the Board, now part of a larger audience, would be entertained by the professor from Cambridge. They would hear, in the long introduction, a plea for support for public education to give rise to institutions "so superior to those of Europe that the European student must come here to finish his scientific education." They would hear a discussion of the facts "which leave no alternative than the conclusion that this Northern Hemisphere has been once covered with a sheet of ice, extending from the arctic regions to the limits where we find connected drift, to latitude thirty-six; and it is to the mechanical action of that sheet of ice we must attribute the source of our soil." Agricultural audiences, by the mid-nineteenth century, had come to expect the speakers to go beyond the range of practical experience. As early as 1822, at the dinner in the Bull's Head Tavern held in connection with the Brighton Cattle Show, Colonel Timothy Pickering had delivered an address that contained a good deal on the science of chemistry.'0 Indeed, practical problems stemming from exhaustion of the rocky New England soils had contributed in large measure to the 9. Agriculture in Massachusetts, 1864, pp. 136-138. 10. Centennial Year 1792-1892; The Massachusetts Society for Promoting Agriculture (Boston: Meader Press, 1942 [reprint]).

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Agassiz, Mendel, and Heredity formation of the Sheffield Scientific School at Yale and the Lawrence Scientific School at Harvard. Science was in the air. Now, with reference to breeding, a century had gone by since Robert Bakewell (1725-1795), in England, had introduced the revolutionary methods that led to formation of improved breeds of livestock and ushered in the modem era of pedigree breeding. Many people had observed dominance, segregation, hybrid vigor. Before 1810 Lord Sommerville, by making the cross between a polled Leicester ram and horned Dorset ewe, had confirmed that the female progeny from such a cross are polled, the males horned."1 John Goss (1787-1833), an Englishman who had to his credit a model of the solar system, a book for teaching the aged and poor to read, and a calculating machine, had observed dominance and segregation in peas in 1820. After separating all the blue peas from the white and sowing each color in separate rows he found that "the blue produce only blue, while the white seeds yield some pods with all white, and some with both blue and white peas intermixed." 12 Goss, who claimed that he learned how to do his work better by reading the Horticultural Society's Transactions (and had a difference of opinion with another correspondent), offered no theoretical explanation for his results. Yet he did perceive that the results were of scientific interest, as shown by the statement: "Should this new variety of Pea neither possess superior merit, nor be deemed singular in its bicoloured produce, yet there is, I conceive, something in its history that will emit a ray of physiological light." 13 Goss had a feeling for his materials and he was modest, but he was not a scientist. Agricultural and horticultural papers of the nineteenth century abound with observations derived from controlled matings and frequently conclude with an appeal to science. For example, an anonymous Missouri contributor of 1832, having observed clear-cut segregation, ends his article as follows: 'We should be glad to receive an explanation of this circumstance from some of our practiced naturalists." 14 Most naturalists were interested in other things, and agriculturists were becoming increasingly concemed with practical affairs. 11. Massachusetts Society for Promoting Agriculture; Papers for 1810 (republication of Lord Sommerville's essay on sheep). 12. A. D. Darbishire, Breeding and the Mendelian Discovery (London: Cassell, 1912), p. 200. Facsimile from the Horticultural Society's Transactions, "On the Variation in the Colour of Peas, Occasioned by Cross Impregnation," in a Letter to the Secretary by John Goss, October 5, 1822. 13. Ibid., p. 200. 14. J. A. Weir, "Amazing Maize," Journal of Heredity, 53 (1962), 99-100. Reprint of "Worldly Matters, Indian Corn," The Evening and the Morning Star, Independence, Missouri 1 (1832), 8.

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In Massachusetts, in 1864, there was still much concem over the serious and often fatal disease of cattle known as contagious pleuro-pneumonia. Percheron horses imported by the Massachusetts Society for Promoting Agriculture had recently arrived and were creating much interest in the state. W. J. Beal (A.B. Michigan 1855), later to distinguish himself in Michigan as a plant breeder and administrator, had another year to go before his Harvard A.B. Nine years would elapse before W. K. Brooks (1848-1908), later to influence T. H. Morgan, E. B. Wilson, and William Bateson, would begin his brief but effective association with Louis Agassiz. Genuine scientific interest in inheritance took a long time to arrive. Unknown to all, in Brunn(now Brno), Czechoslovakia, Gregor Mendel had carried out the crucial experiments. By 1864 his work with peas was finished. The following year the results and theoretical conclusions were presented, and in 1866 they were published.15 When volume 4 of the Proceedings, now a rare book under lock and key, arrived at the MCZ library in 1878, five years after Louis Agassiz' death, no one saw anything in it. And this seems to have been true for the 21 other copies of volume 4 sent to American libraries. III Mendel was a practical horticulturist and beekeeper, pursuits that gave him much pleasure and a solid reputation in the community; he was also a scientist. Today, his reputation rests on a single published work: a concise, factual, 45-page paper based on results from his brilliantly executed experiments in plant hybridization. Mendel died long before others perceived the theoretical consequences of his system which, in the words of Fisher, "he had thought out thoroughly, and in this respect his thought is considerably in advance of that of the first generation of geneticists which followed his rediscovery." 16 In anticipation of the Mendel Centennial and following the several celebrations of the occasion, there have appeared a number of books and essays: Bennett and also Stem and Sherwood have provided valuable source books (the latter contains a new translation of Mendel's famous paper);17 Olby, 15. Gregor Mendel, "Versuche uber Pflanzen-Hybriden," Verhandlungen des naturforschenden Vereines in Brunn, 4 (1866), 3-47. 16. R. A. Fisher, "'Has Mendel's Work Been Rediscovered?" [Originally published in Annals of Science, 1 (1936), 115-137]. Reprinted in Stern and Sherwood p. 166, (see footnote 17). 17. J. H. Bennett, ed., Experiments in Plant Hybridization: Gregor Mendel (Edinburgh: Oliver & Boyd, 1965); Curt Stern and Eva R. Sherwood, ed., The Origin of Genetics: A Mendel Source Book (San Francisco and London: Freeman, 1966).

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Agassiz, Mendel, and Heredity librarian of the Botany School at Oxford, has retraced and added to the materials in Roberts' classic of 1929;18 Crew has returned to and enlarged on the historical approach that once characterized general surveys of genetics;"' Sturtevant, Dunn, Beadle, and others have responded with retrospective analyses.20 It is now clear that significant new additions to Mendeliana are improbable.21 Mendel performed original experiments with plants, particularly the garden pea; he correctly formulated the laws that bear his name and, in Fisher's words, was "fully aware of the importance of what he had done." 22 Additional items-often conjectural, sometimes controversial-mostly relate to periods before or after Mendel's time. Thus we find that Glass sees Maupertuis as a forerunner of Mendel,23 Weinstein argues that Nageli, though he rejected Mendel's discovery, did not fail to understand it;24 Stem would reduce the number of rediscoverers from three to two;25 and Olby gives cogent 18. Robert C. Olby, Origins of Mendelism (London: Constable, 1966); H. F. Roberts, Plant Hybridization Before Mendel (Princeton, 1929; reprint, New York & London: Haffner, 1965). 19. F. A. E. Crew, The Foundations of Genetics (Oxford: Pergamon, 1966). 20. A. H. Sturtevant, A History of Genetics (New York: Harper & Row, 1965); "The Early Mendelians," Proceedings of the American Philosophical Society, 109 (1965), 199-204; "Mendel and the Gene Theory," in R. A. Brink, ed., Heritage from Mendel (Madison; University of Wisconsin Press, 1967). L. C. Dunn, A Short History of Genetics (New York: McGrawHill, 1965); "Mendel, His Work, and His Place in History," Proceedings of the American Philosophical Society, 109 (1965), 189-198; "The Study of Genetics in Man-Retrospect and Prospect," Birth Defects: Original Article Series, 1 (1965), 5-14. George W. Beadle, "Mendelism, 1965," in Brink, Heritage from Mendel. Conway Zirkle, "Some Oddities in the Delayed Discovery of Mendelism," Journal of Heredity, 55 (1964), 65-72. 21. The best biography of Mendel, according to Dunn, is still the one by Hugo Iltis, Gregor Menzdel: Leben, Werk und Wirkung (Berlin: Springer, 1924), Engl. trans. by Eden and Cedar Paul: Life of Mendel (New York, 1932; reprinted by Haffner, 1966); according to Dunn, Oswald Richter and Ingo Krumbiegel add "very little to essential knowledge of the man" (Dunn, "Mendel, His Work and His Place in History," p. 192). Since Iltis' account is sometimes contradictory and draws on interviews with students and associates of Mendel, it should be read in its entirety. New documents have been discovered in Czechoslovakia, some pertaining to Mendel's activities in practical horticulture and agriculture. A serial publication, Folia Mendeliana, under the editorship of V. Orel, Brno, Czechoslovakia, continues to provide opinions and some new facts. 22. Fisher, "Has Mendel's Work Been Rediscovered?" p. 144. 23. H. B. Glass, "Maupertuis and the Beginning of Genetics," Quarterly Review of Biology, 22 (1947), 196-210. 24. Alexander Weinstein, "The Reception of Mendel's Paper by His Contemporaries," Proceedings of the Tenth International Congress of the History of Science, Ithaca (1962), 997-1001 (offprint). 25. Foreword by Curt Stem, Origins of Genetics, p. x. Stem, after carefully reading Tschermak's three papers, concludes that "the designation 'rediscoverer' has only limited validity."

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reasons for thinking that Galton would surely have understood Mendel, an idea that had been advanced many years earlier by East.26 Mendel was a scientist and appeals to scientists of the present day. He was motivated.27 He was well trained in mathematics, physics, botany and chemistry.28 He was a skillful chess player who took delight in devising novel solutions. The monastery was a lively place, with congenial and scholarly colleagues, and had a sympathetic prelate;29 the library was the best in the area. Each of the above items must have contributed something essential to Mendel's success. But why did Mendel become interested in the problems of heredity in the first place, why did he choose the garden pea, and at what stage in his career did he hit upon the particulate theory of inheritance? Can we apply to the young Mendel, before he performed his experiments, the lessons we have learned from them? I think not. Mendel's analytical method was not understood by the practicing naturalists; his curiosity was shared by practical horticulturists and breeders. "Artificial fertilization undertaken on ornamental plants to obtain new color variants initiated the experiments to be discussed here. The striking regularity with which the same hybrid forms always reappeared whenever fertilization between like species took place suggested further experiments whose task it was to follow the development of hybrids in their progeny." Thus did Mendel at the age of forty-three open his address of February 8, 1865, in the clubrooms of the Society 26. Olby, Origins of Mendelism; E. M. East, "Mendel and His Contemporaries," Scientific Monthly, 16 (1923), 225-236. East had this to say of Galton: "But for a matter of mere chance, he probably would have reached the same goal [as Mendel]. The matter of chance was the study of ancestors instead of descendants." 27. Mendel's poetic attempts during his college years have been reexamined by Ludmila Marvanova, "Mendels Dichterische Versuche aus seinen Studentenjahren," Folia Mendeliana, 1 (1966), 15-18. "This poem clearly expresses the enthusiasm of the young student who has for the first time made the acquaintance of scientific books filled with the data of researchers. Mendel admires not only Gutenberg, but every discovery without distinction, any talent of the human mind for invention, and the ability to use the mind" (translated from German). 28. Sturtevant, "Mendel and the Gene Theory," discusses the nature of Mendel's training in Vienna. Mendel studied physics under Doppler and Ettinghausen, botany under Unger, and chemistry under Redenbacher, who was apparently a student of Liebig. 29. Prelate Cyril Franz Napp was quick to recognize talent and to further its development. See Iltis, Life of Mendel. The role of the effective administrator is difficult to assess and even more difficult to document but it can be of crucial importance.

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Agassiz, Mendel, and Heredity Naturforschender Verein. Contrary to popular legend, discussion followed that lecture and also the second lecture on March 8. This has been brought out recently by J. Sajner, whose examination of the 15th volume of a German daily paper in Brno, "Neuigkeiten," revealed that a review appeared the day after each lecture. Evidently the talks, accompanied by demonstrations, made a good impression. The reviews, likely written by Gustav Niessl the mathematician or Alexander Makovsky the botanist, reveal an "appreciation" about on a par with that of subsequent writers who cited Mendel's paper before 1900 (the footnote citation in Schmalhausen's thesis of 1874, in Russian, goes a bit further). Something of the nature of the audience and the functions of the Society of which Mendel was one of the founders may be gleaned from the concluding remarks of the first review, here translated from the German: The great participation of the audience proved that it had been fortunate to propose this lecture, and that the lecture itself had been satisfactory. According to a request by the club's committee it was decided to present the elementary school at Weissenkirchen with a collection of plants and beetles, for which they had asked, and then to get in touch with plant exchange institutes in Vienna and Leipzig in order to replenish the club's herbarium. Finally, the club was enlarged by electing five new members.30 Clearly, Mendel had little reason to expect his audience to grasp the significance of his experiments. Nor could he have expected to fare much better before the Horticultural Society. His remarks on classification concluded with the statement, "In any event, the rank assigned to them [subspecies or species to which the 34 more or less distinct varieties had been assigned by experts] in a classification system is completely immaterial to the experiments in question." It is this sort of statement, for all we know, that may have been a subject for discussion among the naturalists present. Two years later, in a letter to Nageli, Mendel stated: "I attempted to inspire some control experiments, and for that reason discussed the Pisum experiments at the meeting of the local society of naturalists. I encountered, as was to be ex30. Facsimiles of the press accounts of Mendel's talks in Briinn, appearing on February 9 and March 9, are included in a pamphlet, Mendel (without page numbers) distributed at the Mendel Anniversary in Brno, 1965.

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pected, divided opinion; however, as far as I know, no one undertook to repeat the experiments." 81 Failure to convince Nageli may have been, as has frequently been suggested, a great disappointment to Mendel. In any case, those who elected to perform hybridization experiments during Mendel's lifetime proceeded without being inspired by Mendel's work. I have the feeling that Mendel's own flashes of inspiration and his moments of ecstasy occurred at times when he was actively engaged in research in his tiny garden. Truly original ideas in experimental science seldom come from old literature, and it is unlikely that Mendel got his from the works referred to in his paper. As Iltis and Sturtevant have reminded us, Mendel was primarily interested in plants, even though he was also interested in honeybees and kept mice. To me it seems reasonable to conjecture that in his youth Mendel may have observed segregation in farm animals of known parentage and that later he may have made just the right kinds of matings among mice to provide insight into the nature of inheritance. Writers on Mendel have been inclined to ignore or to play down Mendel's work with mice; I may be inclined to go to the opposite extreme (see footnote 37). What did Iltis have to say about Mendel's work with mice? "In one of these rooms [Mendel had two rooms in the monastery] he kept a number of birds; and there was also a cage containing mice which, much to the lad's [Franz Hornisch, student of Mendel] surprise, were ordinary grey mice and not the pretty white mice. Mendel's colleague, Inspector Nowotny, also speaks of the mice kept by Mendel, and it seems probable that they were used in breeding experiments." 32 But further on: "We know from the reports of Hornisch and Nowotny that Mendel used to breed mice in his rooms, grey mice as well as white mice, crossing these varieties. We may plausibly suppose that during these experiments, undertaken perhaps more "for the fun of the thing" than for any profoundly conceived scientific purpose, the phenomena of dominance and separation forced themselves upon his notice. Mendel himself tells us nothing about this matter, making no reference whatever to his experiments on mice. The silence is readily comprehensible. In the eyes of many clericalist zealots it was sufficiently improper for a priest to take any interest in the natural sciences at all, and some persons must have 31. Letter to Carl Nageli, April 18, 1867. In Stern and Sherwood, The Origin of Genetics, pp. 60-61. 32. Iltis, Life of Mendel, p. 92.

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Agassiz, Mendel, and Heredity regarded breeding experiments with animals as positively immoral. Mendel had to walk warily, for (as already said) the bishop had a prejudice against him." 33 There seems no reason to doubt that Mendel did keep mice. What he did with them is a matter for conjecture. Dunn's statement that "he is said also to have bred mice and birds, but there is only indirect evidence of this" 34 strikes me as overly cautious. Iltis' suggestions as to why Mendel gave up mice seem wholly out of keeping with Mendel's character (as portrayed by Iltis). Mendel, the young priest who drew a reprimand from the prelate for attending lectures at the college without a college cap; Mendel, the university student who wrote from Vienna that he would rather be in the primeval forest than attending "the pious exercises"; Mendel, the scientist who never introduced pious reflections into his writings (cf. Agassiz); Mendel, the prelate who stubbornly stuck to his guns in "the struggle for the right," a fight against a tax on religious properties: Was this a man who would give up experiments with mice to ward off possible suspicion? But, as anyone who has bred mice in respectable numbers can testify, it is the animals themselves that offend. Mendel's friends, rather than his enemy the bishop, may have hastened the termination of the experiments. We can have nothing but guess-work about this. If the circumstances surrounding Mendel's place in the history of biology are unclear, surely the contents of his famous paper can be taken at face value. Not so. As shown by Fisher more than twenty years ago and recently confirmed by Wright, Mendel's data are too good by the x2 test.35 Why this is so cannot now be settled, but Wright, Sturtevant, and Beadle have each suggested that the counts of certain classes of peas may have been biased through subconscious errors in favor of expectation.36 Furthermore, Fisher's most important conclu33. Ibid., p. 105. Cf. p. 93 on the experiments with peas: "Langer says that in class he would sometimes give formal demonstrations of the way in which such crossings were effected, showing how the flowers were protected from disturbing influences by paper caps. Yet he did not as a rule explain that he himself was engaged upon such experiments, so that few of his pupils knew that he was an original investigator." Other scattered references also serve to establish that Mendel had a penchant for keeping his own counsel. 34. Dunn, A Short History of Genetics, p. 20. 35. Fisher, "Has Mendel's Work Been Rediscovered?"; Sewall Wright, "Mendel's Ratios," in Stern and Sherwood, The Origin of Genetics, pp. 173-175. 36. Wright, ibid.; Sturtevant, A History of Genetics; Beadle, "Mendelism, 1965." Although Fisher frequently stated that more attention should

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sion-that Mendel had the final interpretation for his ratios clearly in mind before completing his experiments with peasnow meets with widespread acceptance among geneticists.37 Historyhas still not decided why GregorMendel, and Mendel alone, solved the mystery of heredity, nor why he took up the problem in the first place. But the birth (or rather the 1865 stillbirth) of genetics came about through a marriage of horticulture (embodying some of the most primitive of the arts) and physics (generally regarded as the most sophisticated of the sciences). The attraction between the physical sciences and genetics is an interesting one. Not only was Mendel's latent talent first recognized by a physicist, but the encouragement of genetics at Harvard was due to a physicist,38and it was be paid to the history of science, especially by biologists, his own observations generally were intuitive. Even casual reference to Iltis' biography of Mendel would have revealed that Joseph the faithful servant, always on hand with a cloak to shield Mendel from drafts, could not be trusted to collect data so could not have falsified the ratios. Also, Fisher was misled by an error in Roberts' "Plant Hybridization before Mendel," p. 190, as pointed out by Weinstein in "The Reception of Mendel's Paper by his Contemporaries," p. 1001. Nevertheless, Fisher seems to be the only one among thousands of readers of Mendel's paper to actually subject the data to a searching scrutiny. 37. Among the preprints of Folia Mendeliana, Musei Moraviae, 1 (1966), are hitherto unpublished references to Mendel's interest in bees, including E. Lauprecht, "Zur Begegnung von Mendel mit dem Bekannten Bienenzuichter Dathe" pp. 19-22. With practical experience in maintenance of apiaries, dating from his youth on the farm and at the village school, we may be confident that Mendel was conversant with the literature of apiculture. Conway Zirkle, "Gregor Mendel and his Precursors," Isis, 42 (1951), 97-104, points out that Mendel's work may have been stimulated by knowledge of Dzierzon's demonstration that unfertilized F1 queen bees produced a 1:1 ratio of Italian and German drones. Zirkle concludes: .we may be certain that Mendel was acquainted with the work of Knight, of Sageret and of Gartner and probably also knew of Dzierzon's hybrid ratio. In addition he had clues which led to the work of Seton and of Goss. All of these contributions should have aided him in designing his experiments and have alerted him in what to look for." 38. At the Olmutz Philosophical Institute, physics was the subject that most interested Mendel (he did not take the course in agriculture and natural history although he later taught it). The course in physics was taught by Friedrich Franz, who previously had taught at the Philosophical Institute in Brunn and had lived in the Altbriinn monastery. It was Franz who, in 1843, recommended Mendel to Prelate Napp in Brunn. Later, Baumgartner and Doppler took a friendly interest in Mendel and saw to it that he obtained advanced training in physics. At Harvard University the establishment in 1908 of a Graduate School of Applied Science in place of the undergraduate Lawrence Scientific School was the result of a movement led by Wallace Sabine in 1906. Sabine, a physicist whose work in acoustics had raised the design of auditoriums from a primitive state to a reasoned science and precise art, became the school's first dean. W. E. Castle, who had made a reputation outside Harvard and had offers from the

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Agassiz, Mendel, and Heredity Robert A. Milliken, Nobel Prize-winning physicist, who persuaded T. H. Morgan to move from Columbia University to the California Institute of Technology. It is not the function of history to speak of what might have been, but I cannot resist the suggestion that, if Mendel's genius had really become widely understood, Molecular Biology might have dated from the years immediately following World War I instead of World War II. Long-forgotten words of Louis Agassiz serve to recall that the problems of agriculture were a serious concern of midnineteenth-century statesmen, educators, and members of the learned professions. Two generations later, when Mendelism had come into its own, the role of agriculture had changed. Meanwhile, experimental embryology, "experimental evolution," advances in plant breeding, and knowledge of the behavior of chromosomes, had prepared the way for the new science of genetics. For Gregor Mendel, the humble priest, talent, training, a small plot of ground, a sympathetic prelate, and a lively curiosity seemingly were all that were required to uncover the basic laws of inheritance. Finally, it was Agassiz (though it could just as easily have been Mendel) who said: 'Tacts are stupid things until brought into connection with some general law." 39 University of Wisconsin and Yale, impressed Sabine. It was Sabine and president Eliot (the chemist) who saw to it that Castle was provided for in the reorganized Bussey Institution. In moving into an area vacated by agricultural chemistry, genetics attracted men such as E. M. East, Sewall Wright, and R. A. Brink of the Bussey Institute, who had become bored with routine chemical analyses. At Berkeley, R. E. Clausen also came to genetics from chemistry. 39. Samuel H. Scudder, "In the Laboratory with Agassiz," in Lane Cooper, Louis Agassiz as a Teacher (Ithaca: Comstock, 1945), p. 61. [Originally in Every Saturday, 16 (1874), 369-370.1

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The Role of LibertyHyde Baileyand Hugo de Vries in the Rediscoveryof Mendelism CONWAY ZIRKLE Botanical Laboratory, University of Pennsylvania, Philadelphia

The almost simultaneous discovery of the forgotten work of Gregor Mendel by three botanists, working independently, has always called for an explanation. The first one to announce the discovery was Hugo de Vries (1848-1935), who cited it in a paper that was received for publication by the Berichte der deutschen botanischen Gesellschaft on 14 March 1900. The second botanist to announce the discovery was Carl Correns (1864-1933), whose communication was received by the Berichte on 24 April. The third discoverer was Erik von Tschermak (1871-1962), whose paper was received on 2 June. The immediate results of these three papers was that Mendel could no longer be overlooked and that, at last, the importance of his work was recognized. Thus we might say that, in the summer of 1900, genetics was bom. But the birth was long overdue and was by no means easy. There was rivalry and even some ill-feeling among those we may call the attending physicians. The evidence for the ifi-feeling is found primarily in the gossip that was current at the time-gossip that is recorded in some of the personal letters of the discoverers and of their students. De Vries, especially, became the target of much of the talk, and his motives and actions seem to have been questioned because of what might have been an accident in the order of publication. Years later, de Vries had obviously forgotten many of the details of his discovery and, at different times, he gave three different accounts as to how he had been led to Mendel's paper. But these divergent accounts only mean that great scientists, like other human beings, are forgetful. At times, their memories are absent without leave. De Vries himself admitted his memory lapse in a generally overlooked paper that he published in the Revue Gen6ral de botanique (12:257-271, 1900). This paper was dated by de Vries 19 March 1900, just five days after his paper in the Berichte 205

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was received for publication, the paper in which he had announced his discovery of Mendel. In the Revue paper he wrote "This memoir [Mendel'spaper], very beautiful for its time, has been known to me and forgotten." (Ce memoire, trop beau pour son temps, a ete meconnu et ouble). We should also call attention to an earlier and still more overlooked paper that he published in the same volume of the Revue (12:129-137). We shall have occasion to refer to this earlier paper later. One week after de Vries sent his paper to the Revue, he sent his third paper, which he dated 26 March, to the Comptes rendus de l'Academie des Sciences. In this third paper he listed

the Mendelian ratios that he himself had discovered but he did not mention Menders name. This paper and the Berichte

paper were published in the reverse order of their reception and thus the first of all the papers to describe Mendelism did not mention Mendel. This omission actually led some to believe that de Vries wanted the credit of discovering Mendelism and that he did not wish to give credit to Mendel. But when de Vries' paper in the Berichte appeared, the paper that gave full credit to Mendel, this gossip should have been stilled. Sturtevant has described some of the steps taken by the critics to expose de Vries and to show how he had originally intended to take the credit himself for the discovery of Mendelian heredity. Their steps consisted primarily of a search for evidence that de Vries had not mentioned Mendel in the original version of his Berichte paper, but that he had inserted his reference to Mendel when he correctedproof, and after he had discovered that others had also discovered Mendel'swork. As Sturtevant has pointed out, nine of the twenty-two errata listed at the end of the volume of the Berichte concern just the pages that would have had to be altered. The errata are minor but they may have been the result of the printer's having been confused by extensive alterations in the proof. I believe we can discard this notion without further ado. We can now show that de Vries almost certainly knew that Correns had discovered Mendel's paper nearly two months before he submitted his own paper to the Berichte. There is little doubt, however, that several of de Vries' papers were altered in proof, but this is exactly what we would expect in contributions being made to a very active field. De Vries promptly sent a reprint of his Comptes rendus paper to Correns, and this triggered Correns' announcement of his own discovery of Mendel. De Vries, Correns, and von Tschermak all told how they happened to discover Mendel's papers in letters they wrote to H. F. Roberts-letters that Rob206

The Role of Liberty Hyde Bailey and Hugo de Vries erts published in his Plant Hybridization before Mendel. But de Vries' letter shows a memory lapse. The question remains: how and when did de Vries discover Mendel? De Vries, as we have noted, gave three different accounts, and this leads us to Liberty Hyde Bailey (1858-1954). In a letter to Bailey, de Vries stated that he was led to Mendel's work by an item in a bibliography that Bailey had published in 1892. Bailey inserted an excerpt from this letter in a footnote in the later editions of his book, Plant Breeding, a very successful book that went through several editions. De Vries wrote (from the Fourth Edition, 1906, p. 155): Many years ago you had the kindness to send me your article on Cross Breeding and Hybridization of 1892; and I hope it will interest you to know that it was by means of your bibliography therein that I learned some years afterwards of the existence of Mendel's papers, which now are coming to so high credit. Without your aid I fear I should not have found them at all. Some years later, de Vries gave another and different account in the letter he wrote to Roberts. De Vries' letter is dated December 18, 1924: When preparing my book on the Mutation Theory, I worked on the basis of Darwin's Hypothesis of Pangenesis, and of the version of it proposed in my Intracellular Pangenesis. The main principle of Pangenesis is the conception of unit characters. This led on the one side to the theory of the origin of species by means of mutations, and on the other to the description of the phenomena of hybridization as recombinations of these units. In 1893, I crossed Oenothera lamarckiana with 0. lam. brevistylis and found their progeny to be uniform, and true to the specific parent in 1894, but splitting in the second generation 1895, giving 17-26 individuals with the recessive character (Mut. The. 11, p. 157). Many other species were tried with the same result, and dihybrid crosses showed the laws of chance to be valid for them also. After finishing most of these experiments, I happened to read L. H. Bailey's "Plant Breeding" of 1895. In the list of literature of this book, I found the first mention of Mendel's now celebrated paper, and accordingly looked it up and studied it. Thereupon I published in March 1900 the results of my own investigations in the Comptes Rendus de l'Academie des Sciences, p. 845, under the title of "Sur la loi de disjonction des hybrides," and shortly afterwards, in the same year, in the Berichte der deutschen botan-

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ischen Gesellschaft, T. XVIII, p. 83, (March 14, 1900). A full account of my experiments was given in the second volume of the German edition of my Mutation Theory, 1903. Here de Vries' memory is obviously at fault because the source he cited, '"lant Breeding of 1895," does not contain the list of literature that includes Mendel's famous paper on Pisum. It would be well for us, at this point, to recount briefly Bailey's references to Mendel. On December 1, 1891, Bailey gave a lecture entitled "CrossBreeding and Hybridizing" before the Massachusetts State Board of Agriculture in Boston. This was a remarkable lecture in many ways. Bailey's interests were primarily Darwinian and he looked upon the crossing of varieties as a valuable means of securing variations for nature (and man) to select. He also recorded the striking vigor of certain of the hybrids he discussed and, in so doing, he gave us an excellent illustration of how much was known about hybrid vigor (or heterosis) some seventeen years before E. M. East and G. H. Shull brought the subject into the modern genetic picture. This lecture, however, contained no reference to Mendel. Bailey's lecture was published in a monthly periodical, The Rural Library (vol. 1, no. 6) dated April, 1892. This issue was a double number and sold for 40 cents instead of the usual 20 cents. The first part of the periodical consisted of the lecture itself; the latter part was a bibliography listing works on plant hybridization. It consisted of some 450 titles, arranged chronologically. The first item was Paul Dudley's paper of 1724, published in the Philosophical Transactions. The last twentyfour items were dated 1891. Twelve items were dated 1865, and among them was "Mendel, G. Versuche uber PflanzenHybriden, Briinn Verhandl. iv, 3-47." Four items were dated 1869, and these included "Mendel, G. Ueber einige aus Kunstlicher Befruchtung Gewonneren Hieracium-Bastarde. Brunn Verhandl. viii, 26-31." Later, when the importance of Mendel's work was realized, Bailey stated that he had not seen either of Mendel's papers but had merely copied the titles from W. 0. Focke's Die Pflanzenmischlinge (Berlin, 1881). In 1895, Bailey published Plant-Breeding: Being five lectures upon the amelioration of domestic plants. The first and third lectures-"The fact and philosophy of variation," and "How domestic varieties originate"-had been given during the summer to a class in biology at the University of Pennsylvania. The second lecture was the one reprinted from The Rural Library. Lecture four was entitled, '"orrowed Opinions; being 208

The Role of Liberty Hyde Bailey and Hugo de Vries extracts from the writings of B. Verlot, E. A. Carriere, and W. 0. Focke." Lecture five was "Pollination; or how to cross plants." Plant-Breeding did not include the bibliography, nor did it mention Mendel's classical work on peas. Mendel was mentioned, however, in the chapter "Borrowed Opinions" and this citation is indicative. It reads (p. 229) "The various primary forms of the hybrids of Hieracium, Mendel found to be true to seed." Plant-Breeding was a successful book. It was reprinted in 1896 and twice in 1897. In 1902, a second edition was published, and in this edition the famous bibliography was included for the first time. Through an oversight, the fact that the second edition was a second edition was not stated on the title page, so that it might appear to be a mere reprinting of the 1895 issue. This oversight might have led some biologists to ascribe the rediscovery of Mendel's work to the bibliography in Plant Breeding. But here it is worth emphasizing that Plant-Breeding did not include the bibliography until two years after Mendel's work was rediscovered. A third edition of Plant Breeding was published in 1904 and a fourth in 1906, and in these and subsequent editions the bibliography was augmented and brought up to date. So much for Bailey's citations of Mendel. Whatever his role might have been in the rediscovery of Mendelism would have to be traced through the statements and letters of Hugo de Vries. As de Vries wrote in his letter to Bailey, he ascribed his discovery of Mendel to Bailey's bibliography, and this would seem to settle the matter. Certain factors have come to light, however, which complicate this simple picture. The crucial question would seem to be: just when did de Vries read Mendel's paper? In his letter, de Vries wrote merely that he had learned of Mendel's work from Bailey's citation "some years afterwards." Thus we can be sure that de Vries was not led immediately to Mendel's own work by Bailey's inconspicuous citation. The problem is, when did de Vries read Versuche uber Pflanzen-Hybriden? To answer this we can only balance probabilities. But we do have some facts to go on. We know that for over thirty years no biologist who read the paper understood it or recognized its importance. Then, in 1900, three biologists announced its discovery independently and at once the world did appreciate its importance. Once its discovery was announced it served as a basis for the science of heredity. From being almost ignored, it became the center of attention. But it had

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never been overlooked completely; it was just not understood. Hoffmann cited it in 1869. Naegeli was well acquainted with it, as he and Mendel corresponded several times. He missed its meaning although he did list it in the bibliography of Die Hieracien Mittel-Europas, a book he published (1885-1889) with G. A. Peter. W. D. Focke, whose Pflanzenmischlinge (1881) was the source of Bailey's citation, mentioned Mendel and his work fifteen times but showed by his comments that he had missed its significance. Mendel's paper was listed in the Royal Society Catalogue of Scientific Papers and it was mentioned in the article on "Hybridism" in the ninth edition of the Encyclopedia Britannica. The Verhandlung in which Mendel published went to 120 libraries. Recently, Gaissinovitch has called attention to an early citation of Mendel in Russian by I. F. Smalhausen (1849-1894), who took his masters degree at St. Petersburg University in 1874. His dissertation was On Plant Hybrids, and in this study he reviewed Mendel's work in detail in a lengthy footnote because he had discovered Mendel's paper after he had completed his manuscript. VVhen the dissertation was published a second time-and in German-in the Botanische Zeitung (1875) the historical portion, including the summary of Mendel's paper, was omitted. Thus the possibility of an earlier discovery of Mendelism can be described as a near miss. When Mendel published in 1865, however, there was no known biological machinery that could serve as the carrier of his hereditary factors-nothing was known of any particle which passed from generation to generation as did the characters that Mendel described. Cells and cell organs were known but their structures and functions were largely misunderstood. The "cell theory" is generally traced to the work of Schleiden and Schwann in 1839, although cells had been seen and discussed much earlier. This also was the year in which von Mohl described cell division. Earlier, in 1831, Robert Brown had named the nucleus. The fusion of gametes in fertilization had also been recorded and, in 1848, Hofmeister pictured chromosomes in cell division, but he thought that they dissolved and disappeared in resting cells. After Mendel published the longitudinal splitting of chromosomes was established, as was their constant number in the cells of an animal or a plant. The reduction of the chromosome number of one half in the gametes and the restoration of the original number as the gametes fused in fertilization was discovered in the 1880's, and in the middle of the decade a number of leading biologists found in the chromosomes an ideal material basis for heredity.

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The Role of Liberty Hyde Bailey and Hugo de Vries Weismann, in 1887, stated that these must be two kinds of cell division-what we call mitosis and meiosis-and in 1892 he stated that the chromosomes carried the hereditary factors. Thus, when Bailey cited Mendel's paper, the material particles for the transmission of the Mendelian factors were known. Chromosomes passed from generation to generation as did the Mendelian factors. It would have been very difficult for any biologist to have read Mendel's paper in the 1890's and not to have recognized its importance immediately. We know that both Correns and von Tschermak saw its significance and were both busy in composing their verification of Mendelism when de Vries' paper appeared. De Vries had anticipated them but they all published within three months. De Vries' account of his discovery of Mendel's paper is very precise but it is also inaccurate. As we have quoted, he wrote to Roberts that he had observed a second-generation hybrid in an Oenothera cross splitting in 1895, and that after completing these and other experiments he read Bailey's Plant Breeding (1895) and found there "the first mention of Mendel's celebrated paper." The only thing that is wrong with this statement is that no edition of Plant Breeding mentions Mendel's celebrated paper until after de Vries and others had called attention to it. In a later personal communication to R. E. Cleland, he stated that he did not believe that the Mendelian ratios had a universal application [although he had found them in an eleven genera]. Since 1880, he had been investigating Oenothera lamarckiana and had raised over 50,000 plants. On the whole, his Oenothera hybrids had not given Mendelian ratios. But when he read Mendel's paper he had no trouble in recognizing the universal applicability of Mendelism. Both Correns and von Tschermak were led to Mendel's paper by Focke's Pflanzenmischlinge. Ever since its publication in 1881, Pflanzenmischlinge had been the standard work on plant hybridization. As we have stated, Focke referred to Mendel fifteen times and even wrote (p. 110) "Mendel's numerous crossings gave results which were quite similar to those of Knight, but Mendel believed that he had found number-relationships between the types of the crosses." If de Vries had read this statement of Focke's he might well have received a hint that Mendel's ratios might be relevant to those he himself had discovered. Mendel's work might even have seemed to de Vries to be worth a trip to the library. At this point, I would like to insert a personal notion. It is hard for me to believe that de Vries could have read this cita-

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tion of Mendel any time in the 1890's and not have consulted Mendel's paper, or to have read Mendel's paper and not have announced his discovery, certainly with all deliberate speed. When he did describe Mendelism he described it three times in twelve days-twice in French and once in German. that de Vries either We have strong-if indirect-evidence had not read Mendel's paper until a short time before he announced its discovery, or that if he knew of its contents earlier he had not recognized its importance. He called attention to Mendel's work, as we have stated, in his Berichte article and here he was fully aware of Mendel's importance. Our present evidence indicates that de Vries probably had not read Mendel's paper until January 1900 and that he certainly had not read it until sometime after July 1899, because, on 11 July 1899 he gave a definitely pre-Mendelian paper at a symposium sponsored by the Royal Horticultural Society of London. But even in this paper there are complexities. In the autumn of 1898 the Council of the Royal Horticultural Society decided to hold a conference on hybridization. They planned to meet on two days-on 11 July 1899 at Chiswick and on 12 July at the Westminster Town Hall. This was obviously the last pre-Mendelian conference on hybridization. The leading plant hybridizers of the world attended. Both Liberty Hyde Bailey and Hugo de Vries were at the conference and they both gave papers on the first day. Incidentally, there is no record of their having discussed Mendel. De Vries was scheduled to give a paper "Hybridization, as a Means of Pangenetic Infection," but he changed the title to "Hybridizing Monstrosities." In his talk he stated that a very important aspect of pangenesis was that the same character in various organisms depends upon the same material basis. The object of the experiments he described was to demonstrate this by transferring a character from one species to another by means of hybridization. For some years he had kept a hairless form of Lychnis vespertina in his garden and he wished to transmit this glabrous character to L. diurna. The first hybrid generation he obtained was hairy but both hairy and hairless forms appeared in the second generation. In the third generation, those hairless plants that had the other characteristics of L. diurna bred true. The hybrid plants had flowers of different shades and colors but, by selection, de Vries was able to secure a white flowering form that also bred true. On the other hand, plants that had red flowers continued to produce about 6 percent white flowering plants. De Vries had succeeded in synthesizing a new

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The Role of Liberty Hyde Bailey and Hugo de Vries form that bred true-one that he called Lychnis diurna glabra alba. In the paper that he sent to Comptes rendus on 26 March, de Vries had used the terms "dominant" and "recessive," and this usage told Correns that de Vries had read Mendel's paper. In his earlier paper in the Journal of the Royal Horticultural Society, however, these terms were not used, although de Vries had described two true-breeding recessive forms and a dominant form that, mysteriously, continued to segregate. Mendel would have told him that recessives routinely bred true but that there were two kinds of dominants that could be separated easily by inbreeding. One of the dominants would breed true, the other would continue to segregate. De Vries, of course, had a mixture of the two dominants, but he made no attempts to separate them. As we know, some time always elapses between the oral presentation of a paper and its appearance in print. The proceedings of the Hybrid Conference, which contained de Vries' paper, was published in the Journal of the Royal Horticultural Society sometime in 1900, at least six months after the paper was given; perhaps even a longer time elapsed. I believe that there is internal evidence in this article that de Vries first read Mendel's paper between the time that he presented his paper at the Hybrid Conference and the time that he corrected the paper in proof. If this notion is valid, it would date de Vries' discovery of Mendel to within a few months. The evidence on which this notion is based follows. In his printed paper, de Vries refers twice to the 3 to 1 ratio, but he does so somewhat obliquely. The wording is important: I fertilized them in 1893 in the first hybrid generation, when they were all hairy. The hairiness was inherited, as in the red flowering plants, in three-fourths of the individuals, but the white color in nearly every individual (p. 75). Only about three-fourths were hairy, the rest hairless. I had 99 hairy and 54 hairless, in all 153 plants, and counted them in July at the commencement of flowering. The character of the grandfather, the transfer of which I had in view, was therefore once again visible (p. 74). Now, de Vries could have gotten his 3 to 1 ratio either by reading Mendel or by counting his own plants. His own plants, however, did not give a 3 to 1 ratio; 99 to 54 is not a bad 2 to 1 ratio, but is far from a 3 to 1 ratio. These numbers could hardly have led deVries to the discovery of the ratio

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that is routine in Mendelian inheritance. But, on the contrary, if de Vries were aware of Mendel's work, he might see in these figures a chance distortion of the expected ratio. But to recognize this he would have to know what to look for. I believe that de Vries had read Mendel's paper when he corrected the proof of this paper. To recognize a Mendelian ratio for the first time requires a certain amount of plain good luck-luck that, I believe, Mendel himself had. The numbers obtained would have to fit closely to a simple ratio or they would mean very little. In 1868 Charles Darwin reported a ratio of 88 to 37 in two flower types of Antirrhinum, but no one recognized these as a deviant Mendelian ratio. Darwin's figures, in fact, could fit into two very different ratios. If 6 of the recessive had been dominant the ratio would have been 94 to 31, an almost perfect 3 to 1 ratio. On the other hand, if 5 of the dominants had been recessives the ratio would have been 83 to 42, an obvious 2 to 1 ratio. But de Vries listed a still more deviant ratio, a 2 to 1 ratio, as 3 to 1. In his paper in Comptes rendus, de Vries included a table showing the percentages of the recessives as they reappeared in the second hybrid generation. Here he included the two characters of his Lychnis crosses. Lychnis diurna (red) x L. vespertina (white) gave 27 per cent recessive, while L. glabra (smooth x L. vespertina (pubescent) gave 28 per cent. But in his paper in the Journal of the Royal Horticultural Society, the recessive Lychnis appeared in 35.3 per cent. As Sturtevant has noted, de Vries, in his paper in the Revue that he dated 19 March 1900, mentioned Mendel only briefly and on the last page. We have documentary evidence, however, that de Vries knew of Mendel when he submitted another paper that was published earlier in the same volume. The previous year-in 1899-S. Nawaschin had described double fertilization and had shown that the endosperm contained one of the male nuclei. Here was the first cytological explanation of xenia. This was exciting news to the plant hybridizers, and de Vries shortly thereafter published his work on the endosperm of his hybrid Zea mays. The hybrid in question was between a corn with starchy grains and a corn with sugary ones, and was illustrated by an excellent plate. In a segregating ear, de Vries reported 180 starchy to 66 sugary grains, an almost perfect 3 to 1 ratio. He also counted the grains on 35 ears and reported: "Environ un quart des grains etaient suicres, les trois, autres quarts etaient amylac6s". The starchy grains segregated and produced one fourth sugary.

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The Role of Liberty Hyde Bailey and Hugo de Vries Now to the direct evidence that de Vries knew of Mendel when he wrote the above! This takes us to his rival and enemy, Carl Correns. Both Correns and de Vries were working on xenia in Zea mays when Nawaschin's work appeared. Correns had submitted a paper on the subject to the Berichte on 22 December 1899. It was reported in the session of the Society on 29 December and published in the Berichte on 25 January 1900. In the last paragraph of this paper, Correns stated that the color of the individual peas, which he had also hybridized, was the color of the embryo and not the color of the endosperm, "as already pointed out by Darwin and Mendel." Did this paper tell de Vries that Correns also knew of Mendel? Sturtevant has suggested that if this were the case it would be the simplest interpretation of the puzzling facts, but that this conclusion cannot be accepted as established. We can now say that it can be established. De Vries knew of this paper of Correns and listed it in a footnote on the first page (p. 129) of his first paper in volume XII of the Revue: "M. C. Correns, de Tubingue, a publie le meme resultat dans les Berichte der d. botan. Gesellsch, Bd. XVII Heft 10. Seance du 29 dec. 1899, p. 410. We also have reliable testimony that de Vries was led to Mendel's paper by neither Bailey nor Focke. Professor Th. J. Stomps, who succeeded de Vries at the Botanical Institute at Amsterdam, has given us the details. De Vries has found Mendelian segregation but had not recognized its universality. Mendel's paper, however, had put the matter in a different light. According to Stomps, in 1900, at just the time de Vries was about to publish his results, he received a letter from his friend Professor Beyerinck at Delft that read, "I know that you are studying hybrids, so perhaps the enclosed reprint of the year 1865 by a certain Mendel, which I happen to possess, is still of some interest to you." Professor Stomps goes on to state: This then is the true story of the rediscovery of Mendel. I once asked de Vries whether he could remember the precise moment at which he discovered Mendel's now famous paper, and he personally related the story to me. After the death of Beyerinck, I received remarkable proof of the exactness of his words: his family sent the reprint in question again to our institute, this time to me as director, with the words that the right place would be the library of the Botanical Institute at Amsterdam, where indeed one can see it today in a special showcase.

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De Vries has given three incompatible accounts as to the clues that led to his discovery of Mendel's paper. The preponderance of evidence would seem to favor the account quoted by Stomps. There remains the question, however, of why de Vries wrote his very polite letter to Bailey. It is rather unusual, of course, for any botanist to be spontaneously polite to any other botanist, but when de Vries wrote to Bailey, he may merely have been forgetful and in a kindly mood. It would also indicate that he had been aware of Mendel sometime before either Correns or von Tschermak. This is not the place to record the various alarms and excursions that occurred, mostly off-stage, in the reactions of the three discoverers of Mendel, such as the reputed behavior of Correns when he received de Vries reprint on 21 April, or of the brief spat between Correns and von Tschermak when they met in 1903. How the discoverers reacted to each other is relevant, however, to the many misunderstandings that followed their discoveries. Correns and von Tschermak soon "buried the hatchet" but not in each other's skulls. In a lecture in Vienna in June 1950 (published twice in 1951) von Tschermak stated (Journal of Heredity 42: 167): It is interesting to note that de Vries apparently became quite jealous of the rapid development of Mendelism, and considered his mutation theory somewhat ignored, especially among breeders. Only such a jealousy can explain the fact that he did not even mention Mendel's name in his 1907 book Pflanzenzuchtung [Plant Breeding] and his brusque refusal to sign a petition for the erection of a Mendel memorial in Brunn in 1908. There is no doubt that de Vries was one of the great biologists of the late nineteenth and early twentieth centuries. There is also no doubt that he later became very proud of the fact that he was one of the discoverers of Mendel. Summary 1. The almost simultaneous and overlapping discoveries of Mendel's forgotten work by Hugo de Vries, Carl Correns, and Erik von Tschermak gave rise to an intense rivalry, some jealousy, and more than a little illfeeling. De Vries, the first to announce the discovery, has been subjected to the charge that he wished to conceal his discovery and to obtain for himself the credit for having discovered what we now call Mendelism. This charge involves the statement that de Vries gave credit to Mendel only after he had found that others had also read Mendel's papers. The evidence on which this charge is based is sketchy, and we can now show that at least that portion of it that is based on supposed alteration in the proof of de Vries' paper in the Berichte is without foundation. Unfortun-

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The Role of LibertyHyde Bailey and Hugo de Vries ately, de Vries gave three different accounts of how he was led to Mendel's work. Two of these involve Liberty Hyde Bailey. 2. Bailey had listed Mendel's papers in a bibliography that he published in 1892 in The Rural Library. Bailey did not include this bibliography in the first edition (1895) of Plant Breeding or in its reprinting in 1896 and 1897. He did include the bibliography in the second edition (1902), but this was after de Vries and others had called attention to Mendel. In 1899, both Bailey and de Vries gave papers at the Hybrid Conference held at Chiswick, England, but we have no record of their having discussed Mendel. What evidence we have indicates that, at this time, neither of them had read Mendel's papers. 3. De Vries wrote to Bailey that it was Bailey's listing of Mendel in the bibliography published in The Rural Library that led to his discovery of Mendel. Later, de Vries wrote to H. F. Roberts that he had first found a reference to Mendel in Bailey's Plant Breeding of 1895, where the bibliographic reference to Mendel's papers was not published. Finally, de Vries told Th. J. Stomps, who succeeded him at the University of Amsterdam, that he had first learned of Mendel early in 1900 from a reprint of Mendel's paper sent him by his friend Professor M. W. Beyerinck. Our present evidence favors Stomp's account as it shows that de Vries had not read Mendel's papers in 1899 but had early in 1900. 4. Attempts to pinpoint de Vries' discovery of Mendel are aided in part, and in part confused, by the fact that he published five relevant papers in 1900. These papers were in press simultaneously, and some of them were altered in proof. Further confusion is due to the fact that at least three of them were published in the reverse order of their acceptance for publication. Unfortunately we do not have the crucial dates for all of the papers. a. J. Roy. Hort. Soc. 24:69-75. A definitely pre-Mendelian paper given on 11 July 1899, and published in 1900 (possibly in April). The evidence for an alteration in proof after de Vries had read Mendel is shown by the fact that de Vries described a ratio of 99 to 54 as a 3 to 1 ratio. b. Rev. g6n. botan. 12:129-137. A Mendelian paper, giving the 3 to 1 ratio in the F2 generation of a cross between starchy and sugary corn. The paper is not dated by de Vries but it was published in the volume, 128 pages ahead of a paper de Vries dated 19 March. In a footnote, de Vries cites a paper by Correns that was published on 25 January, so we can tell that it was written or corrected in proof after this date. Here Correns showed de Vries that he had already read Mendel's paper. Any attempt by de Vries to ignore Mendel or get credit for Mendelism after 25 January would have been senseless. This date was nearly two months before de Vries' Berichte paper was submitted for publication. c. Ber. deut. botan. Ges. 18:83-90. Accepted for publication 14 March, published 25 April. This paper gives Mendel full credit and stimulated the publications of Correns and von Tschermak. As de Vries was aware that Correns already knew of Mendel when the paper was first submitted, there was no occasion to alter it in proof. d. Rev. gen. botan. 12:257-271. Dated by de Vries 19 March, but the proof was read after June. De Vries cites von Tschermak's paper in the Berichte that was published in June. The Revue paper is a Mendelian paper, and Mendel is cited on the last page. e. C. R. Acad. Sci. (Paris) 130:845-847. Accepted for publication 26 March 1900. Reprint received by Correns 21 April. Mendel is not mentioned but de Vries' use of terms told Correns that de Vries had read Mendel's paper. First of the papers to be published, it caused Correns to assume that de Vries wanted the credit that was due Mendel.

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5. The three discoverers of Mendel did not form a mutual admiration society. BIBLIOGRAPHY Bailey, L. H. "Cross-breeding and Hybridizing," The Rural Library, 1 (1892), 1-44. Plant Breeding. New York. 1895. Correns, C. "Untersuchungen uber die Xenien bei Zea Mays," Ber. deut. botan. Ges., 17 (1900), 410-418. "G. Mendels Regel iiber das Verhalten der Nachkommenschaft der Rassenbastarde," Ber. deut. botan. Ges., 18 (1900), 158-168. Dunn, L. C. A Short History of Genetics. New York, 1965. Focke, W. G. Die Pflanzenmischlinge. Berlin, 1881. Gaissinovitch, A. E. "An Early Account of G. Mendel's Work in Russia," in C. Mendel Memorial Symposium, ed., Milan Sosna. Prague, 1966. Hofmeister, W. Ober die Entwickelung des Pollens," Botan. Ztg., 6 (1848), 425-434. Nawaschin, S. "Neuen Beobactungen uber Befruchten bei Fritallania tenella und Lilium Martagon," Botan. Centralb., 77 (1899), 62. Roberts, H. F. Plant Hybridization Before Mendel. Princeton, N.J., 1929. Sirks, M. J., and Conway Zirkle. The Evolution of Biology, New York, 1964. Stomps, Th. H. "On the Rediscovery of Mendel's Work by Hugo de Vries," J. Heredity, 45 (1954), 293-294. Sturtevant, A. H. A History of Genetics, New York, 1965. von Tschermak, E. "Ober kunstlicke Kreuzung bei Pisum sativum," Ber. deut. botan. Ges., 18 (1900), 232-239. "The Rediscovery of Gregor Mendel's Work," J. Heredity, 42 (1951), 163-171. de Vries, Hugo. "Hybridizing Monstrosities," J. Roy. Hort. Soc., 24 (1900), 69-75. "Sur la loi de disjunction des hybrides," C. R. Acad. Sci. (Paris), 130 (1900), 845-847. "Das Spaltungsgesetz der Bastarde," Ber. deut. botan. Ges., 18 (1900), 83-90. "Sur la f6condation hybride de l'endosperme chez le mais," Rev. gen. botan., 12 (1900), 129-137. "Sur le unities de caracteres sp6cifiques et leur application a l'etude des hybrides," Rev. gdn. botan., 12 (1900), 257-271. Weismann, A. Ueber die Zahl der Rictungs khrper. Jena, 1877. Das Keimplasma. Jena, 1892. Zirkle, Conway. "Gregor Mendel and His Precursors," Isis, 42 (1951), 97-104. "Some Oddities in the Delayed Discoveries of Mendelism," J. Heredity, 55 (1964), 65-72.

218

Mendel'sProgramfor the Hybridizationof Apple Trees V. OREL Gregor Mendel Department, Moravian Museum, Brno, Czechoslovakia M. VAVRA Pomiculture Institute, the College of Agriculture Brno, Czechoslovakia

According to Iltis,l Gregor Mendel, besides experimenting with peas, also devoted a good deal of time to the hybridization of fruit trees, vegetables, and flowers, raising the resulting seedlings with utmost care and sometimes grafting them on older trees. Iltis also refers to the notes in Mendel's own handwriting in John, Lukas, and Oberdieck's illustrated Handbuch der Obstkunde. In searching for all the documents connected with this activity of Mendel, we have found conclusive evidence that he was not only carrying out his hybridizing experiments with flowers, but also with different kinds of vegetables, and especially with fruit trees. KMiwanek,2describing the history of the Pomicultural, Wine-Growing, and Horticultural Societies in Brno in 1898, mentions that Mendel was interested in improving different kinds of fruit trees and flowers by hybridization and that he was successful with some pommes and with fuchsia. The article in memory of Gregor Mendel, published in 1884 by the Horticultural Section of the Moravian and Silesian Agricultural Society, informs us that he took part in an exhibition of vegetables as early as 1859, and that his exhibition attracted attention. As an active member of the Horticulture Section he supported the organization of regular exhibitions of fruit, vegetables and flowers in Brno and used to offer prizes for the 1. H. Iltis, Gregor Joh)ann Mendel, Leben, Werk und Wirkung (Berlin; J. Springer Verlag, 1924). 2. L. Kriwanek and T. Suchanek, Geschichte des Mahrischen Obst-, Wein- und Gartenbauvereines (Brinn, 1898).

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M. VAVRA

best improvement by hybridization. Even in the autumn of 1883, a few months before his death, at a meeting of the Austrian Pomological Society, he was awarded in absentia the medal of the Hietzing Horticultural Society for his exhibit of new varieties of apples and pears. The report of the exhibition from the year 1882 informs us that that year a collection of new varieties of peas had been awarded the first prize, but that the exhibitor from Brno, an active member of the Society, had not accepted it and asked that his name not be mentioned. In the report of the exhibition there are three crosses in place of the name of the exhibitor. We are convinced that this exhibitor was Gregor Mendel, who was acting as a member of the judging committee and who never personally accepted any awards. The most interesting documents we have found deal with a program of hybridization of apple trees and pear trees prepared by Mendel and written in his own handwriting in the 1859 copy of "Illustriertes Handbuch der Obstkunde." 3 There are also notes dated 1881, only two years before his death. Besides this program of hybridization there are also some other notes to the text on various pages of the book which testify to the fact that Mendel studied it in detail. We shall try to analyze his program for the hybridization of apple trees and to explain the goal we suppose he was interested in reaching. The program contains 12 varieties as mother plants and 17 as pollen plants, a total of 30 different crossing combinations. All these combinations are summarized in Table 1, at the end of this paper. In the case of these crossings Mendel probably wanted to improve the varieties of apples by connecting the best characters from both crossed varieties. In most instances he was interested in combining the best qualities of taste with resistance to climatic conditions, especially regarding modest requirements of soil and height of location. As an illustration, combination No. 9 of Table 1 may be mentioned: Roy Fruit Cultiv. (Graue franzosische Reinette) x Susser Holaart. The mother apples from the mother variety Roy Fruit Cultiv. attain best quality only when grown in warm locations and under first-class soil conditions. In colder and rougher locations the apples are without taste and the trees suffer from cancer. The apples from the pollen variety Siisser Hollart are also sweet but of lower taste quality. This fruit tree also blos3. F. Jahn, E. Lucas, and J. G. G. Oberdieck, Illustriertes Handbuch der Obstkunde. I. Aepfel (Ravensburg, 1865); IV. Aepfel (Ravensburg, 1865); VIII. Aepfel (Stuttgart, 1875).

220

FIG. 1. Two views of the medal awarded to Mendel for his exhibit of new varieties of apples and pears in Brno, Czechoslovakia, in 1882. At the left the goddess "Pomona" distributes flowers and fruits to human industry, represented by two small boys. These photographs of the medal by Pla'nava have not been published before.

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FIG. 2. The program of the hybridization of apple trees, prepared and written by Mendel in the copy of the Illustriertes Handbuch der Obstkunde by F Jahn E. Lucas, and J. G. G. Oberdiek (Stuttgart, 1875).

Mendel's Programnfor the Hybridization of Apple Trees soms much later and is therefore suitable for colder and rougher conditions and has a lower requirement of soil quality. In other combinations, Mendel was interested in improving the qualitative characters by crossing those varieties of apples which are noted for nearly equal qualitative characters, as, for example, combination No. 8, Reinette de Canada X White Winter-Calvill. Reinette de Canada, as the mother variety, produces apples of highest quality which are very similar to the apples from the pollen variety White Winter-Calvill. In this case Mendel could not have been interested in finding a single combination of two different factors and thus connecting the characters of both varieties. In his classic paper on Phaseolus experiments he tried to explain the heredity of the characters in flower color.4 He came to the conclusion that this character was determined "by the independent hereditary factors" (Elemente) Al and A2, each of which was acting by itself, competent to determine the production of a particular shade of red. Later, in his experiments with Matthiola, he explained this kind of heredity as "the outcome of the simultaneous operation of several heredity factors." 5 In modem genetic theory this phenomenon is explained by the harnonious interaction of genes. That he probably could have achieved a similar purpose by increasing the character of the apple core in combinations 1, 2, and 3 (Table 1) is confirmed by the note to combination No. 2 "cicad" (water-cored) and by the connecting of characters presumed as single forms ("Vermuthe einfache Form") in the case of combination No. 1. In this way he could breed a new variety, the product of which would be noted for qualitative characters higher in a certain respect than the products from both parental varieties. Combination No. 5 represents a special kind of combination of varieties, that in which we can see reciprocal crossing. The mother variety Willy had been cultivated by hybridizing White Winter-Calvill and White Winter-Calvill. This variety is of first quality, similar to the quality of the pollen variety plant. In this case Mendel could have been interested in improving the quality of these varieties by the cumulation of the "heredity factors" by means of reciprocal crossing, and, we can say, by means of inbreeding. Mendel's program of hybridizing apple trees is surely of great interest. We are, of course, not able to explain in detail his intention of improving these varieties of apples, but have 4. G. Mendel, "Versuche iTber Pflanzenhybriden," Naturforschenden Vereines, 4 (1886), 3-47. 5. Ibid.

Verhandlungen

221

des

M. VAVRA

V. OREL

tried to explain his intention in some typical kinds of combinations in terms of the genetic knowledge in his papers and by his notes in the Illustriertes Handbuch der Obstkunde.

These notes testify that up to the close of his life Mendel never lost his interest in pomiculture and in hybridization,an interest which had been awakened during his childhood when he used to collaboratewith his father in the orchard surrounding his native house at Hyncice (Heinzendorf). Table 1. Mendel'sprogram for the hybridizationof apple trees Mothervariety

Pollen variety

1. White Astracan (Weisser Astracan)

Foxley Russian Apple (Sommer Gewurzapfel)

2. White Astracan (Weisser Astracan)

Der Kostlichste(Bozen)

3. BurchardtCarolin

White Astracan (Weisser Astracan)

4. Alant Apple (Alantapfel)

White Winter-Calvill (Weisser Winter-Kalvill)

5. Willy

White Winter-Calvill (Weisser Winter-Kalvill)

6. Calvill de Neige (Schnee Kalvill)

Garibaldi'sCalvill (GaribaldisKalvill)

7. Winter Postoph

White Winter-Calvill (Weisser Winter-Kalvill)

8. Reinette de Canada (KanadaReinette)

White Winter-Calvill (Weisser Winter-Kalvill)

9. Roy Fruit Cultiv. (Graue franzosische Reinette)

Susser Holaart

10. Roy Fruit Cultiv. (Graue franzosische Reinette)

Stetting Rouge (Roter Stettiner)

11. Roy Fruit Cultiv. (Graue franzosische Reinette)

Dutsch Mignon (Grosse Kasseler Reinette, Laak Pomme)

222

Mendel's Program for the Hybridization of Apple Trees Table 1 (continued) Mother variety

Pollen variety

12. Roy Fruit Cultiv. (Graue franz6sische Reinette)

Der Kostlichste (Bozen)

13. Roy Fruit Cultiv. (Graue franzosische Reinette)

White Winter-Calvill (Weisser Winter-Kalvill)

14. Roy Fruit Cultiv. (Graue franz6sische Reinette)

Bordsdorfer (Edelborsdorfer)

15. Roy Fruit Cultiv. (Graue franzosische Reinette)

Rouge Winter Pigeon (Roter Winter-Taubenapfel)

16. Roy Fruit Cultiv. (Graue franz6sische Reinette)

Alant Apple (Alantapfel)

17. Suisser Holaart

Champagner Reinette

18. Siusser Holaart

Dutsch Mignon (Grosse Kasseler Reinette, Laak Pomme)

19. Siusser Holaart

Stetting Rouge (Roter Stettiner)

20. Susser Holaart

White Winter Taffetapfel (Weisser Winter Taffetapfel)

21. Siusser Holaart

Borsdorfer (Edelsborsdorfer)

22. Siusser Holaart

White Winter-Calvill (Weisser Winter-Kalvill)

23. Susser Holaart

Roode Peasch Apple (Roter Oster-Kalvill)

24. Champagner Reinette

Foxley Russian Apple (Sommer Gewurzapfel)

25. Champagner Reinette

Siissfranke

26. Dietzer Goldreinette

Orleans Reinette 223

V. OREL

M. VAVRA

Table 1 (continued) Mother variety

Pollen variety

27. Margil Hook. (Muscat Reinette)

White Astracan (Weisser Astracan)

28. Margil Hook. (Muscat Reinette)

Oberdiecks Reinette

29. Margil Hook. (Muscat Reinette)

Barsdorfer (Edelborsdorfer)

30. Calvill de Neige (Schnee Kalvill)

White Winter Taffetapfel (Weisser Winter Taffetapfel)

224

Studiesof AnimalPopulationsfrom Lamarckto Darwin FRANK N. EGERTON Hunt Botanical Library Carnegie-Mellon University, Pittsburgh, Pennsylvania

Though ecology is a modern science, certain ecological questions have always received at least passing attention from those who have taken an interest in plants and animals. For example: Is a particular species terrestrial or aquatic? Does it live in a cold or a hot climate? What does it eat (if an animal) and what eats it? What causes the sudden appearance of a plague of locusts or rodents? Yet passing attention is not enough for the founding of a science. Scientific investigators must feel that such questions merit detailed answers, and the information they acquire must be synthesized into a coherent body of knowledge that is generally accepted by the practitioners of that science. Professor Kuhn has called such a synthesis a paradigm,' and he has judged its emergence as an indication of the maturity of a science. In animal ecology, the book which first met this description was Professor Charles Elton's Animal Ecology (London: Sidgwick and Jackson, 1927, xi + 204 pp.), which had gone through nine printings by 1962. Kuhn has also observed that usually the paradigm can only be written after arduous work in a science.2 The present paper describes developments in one area of ecology during part of its pre-paradigm history. Following Kuhn's analogy, the period under discussion is equivalent to late adolescence, for it included the abandonment of previously accepted superficial answers, a growing realization of the complexity of ecological phenomena, and the establishment in biology of a theoretical framework which would both make ecological information more usable than it had been before and provide a more effective point of view for making ecological observations. 1. Thomas S. Kuhn, The Structure of Scientific Revolutions University of Chicago Press, 1962), p. 10. 2. Ibid., p. 15.

(Chicago:

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FRANK N. EGERTON

During the period from 1800 to 1860, a central issue in biology was whether the living world was as stable as had been generally believed since antiquity. If the answer was no, then to what extent was stability an illusion, and how could one explain the existence of certain amounts or kinds of both stability and change? Few scientists of that time could or would have posed the question so broadly, but most of them were aware of the questionings of the old static explanations. The balance of nature was an implicit assumption that had seldom, if ever, been questioned.3 Animal plagues were familiar distortions of this presumed balance, and the study of them might have provided new ways to re-examine this old assumption. However, although naturalists in the eighteenth century had contributed many observations toward the understanding of animal populations, they had not synthesized effectively the accumulated information.4 Thus they responded weakly to Malthus' ideas on population pressure. It had long been known that many species produced impressive numbers of offspring, but this fact was seen merely as a device for insuring the preservation of the species and the balance of nature. Naturalists seemed to have believed that competition was neither severe nor pervasive in nature, but no one seems to have investigated the situation deeply enough to have had a strong response to Malthus. Demographic data for animals were difficult to collect systematically, and it was not yet clear what kinds should be collected or how they should be used even if collected. There were, nevertheless, some attempts made before Darwin to integrate demographic information on longevity, reproductive capacity, and population pressure into broader biological discussions. Lyell's was the most successful of these efforts. 3. The origins of this concept are discussed in my paper on "Ancient Sources for Animal Demography," Isis (in press). 4. Statements about animal demography in the eighteenth century are based upon ch. 3 of my dissertation, submitted in 1967 to the University of Wisconsin in partial fulfillment of the requirements for the Ph.D. degree. It is entitled "Observations and Studies of Animal Populations before 1860; A Survey Concluding with Darwin's Origin of Species." It was written under the direction of Professor Robert Clinton Stauffer, to whom I wish to express my appreciation for his assistance. The present paper is based upon chap. 4 of this dissertation. I wish to thank Professors William Coleman of Johns Hopkins University and Harold L. Burstyn of CarnegieMellon University for their suggestions on preparing this paper for publication. For a general sketch of the history of animal ecology, see W. C. Allee, "Ecological Background and Growth Before 1900," in W. C. Allee, A. E. Emerson, Orlando Park, Thomas Park, Karl P. Schmidt, Principles of Animal Ecology (Philadelphia and London: W. B. Saunders, 1949), pp. 13-43.

226

Studies of Animal Populations from Lamarck to Darwin Only Darwin and Wallace, however, were able to explain how the biology of populations plays a significant role in that process which gradually but continually alters animate speciesevolution by natural selection. Because of the great importance of Darwin's contribution to animal demography, this paper falls naturally into two parts. The first shows the development in the early nineteenth century of ideas about population pressure, competition, extinction, biogeography, and biological communities. The second part shows how all of these ideas became ingredients in Darwin's theory of evolution. The discussion will also indicate how his theory laid the foundation for modem interests and developments in animal demography, but the actual treatment of this topic is beyond the scope of this paper. I. DEVELOPMENTS BEFORE DARWIN A. Extinction vs. Evolution Although naturalists were not yet ready by 1800 to assess the significance of Malthusianism, they were prepared to settle a question of longer standing which had significance for animal demography: whether or not species have ever become extinct. Both Georges Cuvier (1769-1832) and John Playfair (17481819)5 effectively argued that species do become extinct. Cuvier pointed out that fossils seldom resemble modern species. Since he failed to find intermediate forms between living and fossil species,6 he rejected the possibility of evolution and concluded that many species had become extinct.7 The weight of his judgment had an important influence upon the opinion of other scientists. As Eiseley has remarked, there was a rapid shift in the consensus of scientists from the belief that species could not become extinct to the belief that species are periodically exterminated.8 Although this new conclusion had important implications for the study of animal population dy5. Playfair, Illustrations of the Huttonian Theory of the Earth (Edinburgh, London: William Creech, Cadeil and Davies, 1802; facsimile eds. Urbana: University of Illinois Press, 1956; New York: Dover Publications, 1964), pp. 458-476. 6. Cuvier, "Discours preliminaire," in Recherches sur les ossemens fossiles de quadrupeds, 4 vols. (Paris: Deterville, 1812; 2nd ed., Paris: Dufour et d'Ocagne, 1821-24; citations from 1st ed.), vol. 1, p. 74. Eng. trans. by Robert Kerr as Essay on the Theory of the Earth, with Mineralogical Notes and an Account of CuvieT's Geological Discoveries by RobeTt Jameson (Edinburgh, 1813; 5th ed., Edinburgh: W. Blackwood, 1827; citations from ed. New York: Kirk and Mercein, 1818), p. 119. 7. Cuvier, "Discours," p. 39. Eng. trans., p. 75. 8. Loren Eiseley, The Firmament of Time (New York: Atheneum, 1960), pp. 35-51.

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namics, these implications received little immediate attention. The altermativeconclusion, that species had evolved and the living ones could no longer be identified with their fossil ancestors,was defendedby Lamarck(1744-1829). Organicevolution implies that animate nature is in a constant state of change, but Lamarckwas unwilling to push his concept to its logical extreme. In fact, his writings on evolution offered a reaction to the consensus on the extinction of species, and far from emphasizing change in nature, he saw evolution as a means of preserving ecological, if not morphological,stability: As a result of the rapid multiplicationof the small species, and particularly of the more imperfect animals, the multiplicity of individuals might have injurious effects upon the preservationof races, upon the progress made in perfection of organisation, in short, upon the general order, if nature had not taken precautions to restrain that multiplication within limits that can never be exceeded. Animals eat each other, except those which live only on plants; but these are liable to be devoured by carnivorous a

ls.

We know that it is the stronger and the better equipped that eat the weaker, and that the larger species devour the smaller. Nevertheless, individuals rarely eat others of the same race as themselves; they make war on different races. The multiplication of the small species of animals is so great, and the succession of generations is so rapid, that these small species would render the globe uninhabitable to any others, if nature had not set a limit to their prodigious multiplication. But since they serve as prey to a multitude of other animals, and since the duration of their life is very short and they are killed by any fall of temperature, their numbers are always maintained in the proper proportions for the preservationof their own and otherraces. As to the larger and stronger animals, they might well become dominant and have bad effects upon the preservation of many other races if they could multiply in too large porportions; but their races devour one another, and they only multiply slowly and few at a time; and this maintains in their case also the kind of equilibriumthat shouldexist. By these wise precautions, everything is thus preservedin the established order; the continual changes and renewals which are observed in that order are kept within limits that they cannot pass; all the races of living bodies continue to 228

Studies of Animal Populations from Lamarck to Darwin exist in spite of their variations; none of the progress made towards perfection of organization is lost; what appears to be disorder, confusion, anomaly, incessantly passes again into the general order, and even contributes to it; everywhere and always the will of the Sublime Author of nature and of everything that exists is invariably carried out.9 Lamarck's writings do not indicate that he had much firsthand knowledge of population dynamics. Although his theory of evolution had some novelty, he used it in the foregoing passage to defend the old concept of a balance of nature. He was convinced that organisms have the capacity to change to meet new environmental challenges and to pass on their physical changes to their offspring.10 Since he believed that organisms respond quickly to environmental changes, he concentrated upon physiology and neglected ecology. His conclusion contained a part of the truth-some species do evolve into new species. However, since Lamarck had overestimated the adaptability of species to new environmental demands, his theory of evolution, unlike Darwin's, led to a worse rather than a better understanding of population biology. Lamarck's ideas concerning population were minor supports for his highly controversial theory of evolution, and his contemporaries reacted against the theory itself rather than against this particular supporting argument. Cuvier, who rejected the idea of evolution, preferred to discuss the question from the viewpoint of his specialty, comparative anatomy." His few lecture notes dealing with population show that he also had not thought much about the subject.'2 9. Lamarck, Philosophie zoologique, ou exposition des considt6rations relatives a I'histoire naturelle des animaux; el la diversit4 de leur organisation et des facultcs qu'ils en obtiennent; aux causes physiques qui maintiennent en eux la vie et donnent lieu aux mouvements qu'ils ex.6cutent; enfin, a celles qui produisent, les unes les sentiments, et les autres l'intelligence de ceux qui en sont dou6s, 2 vols. (Paris: Dentu, 1809; 2nd ed., 1830; 3rd ed., 1873; citations from 1st ed.), pt. 1, ch. 4, pp. 99-101. Eng. trans. by Hugh Elliot as Zoological Philosophy; An Exposition with Regard to the Natural History of Animals (London: Macmillan, 1914), pp. 54-55; facsimile reprint (New York and London: Hafner, 1963). 10. Against the idea of extinction: Phil. Zool., pt. 1, chap. 3, pp. 75-77; Eng. trans., pp. 44-45. Modifications from changing environment: Phil. Zool., pt. 1, chap. 7, pp. 221ff.; Eng. trans. pp. 106ff. Laws of evolution and heredity: Phil. Zool., pt. 1, chap. 7, pp. 233-268; Eng. trans., pp. 113126. 11. William Coleman, "Georges Cuvier, Biological Variation and the Fixity of Species," Archives internationales d'histoire des sciences, 15 (1962), 315-331. 12. Quoted by Coleman, "Cuvier," p. 320, note 14. See also William Coleman, Georges Cuvier, Zoologist. A Study in the History of Evolutionary Theory (Cambridge, Mass.: Harvard University Press, 1964), p. 160.

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FRANK N. EGERTON

He believed in the balance of nature as confidently as did Lamarck. Cuvier believed that extinction was caused by geological catastrophes, such as the elevation and subsidence of land.13 Since these past land movements could not be described with any precision, his ideas about extinction were not developed in any detail. Nor did he make any serious connection between his ideas on land movement and biogeography. His passing remarks on the latter subject were as superficial as those on population.14

B. Biogeography The species question was not resolved by Cuvier's anatomical observations and theories. The subject had also to be attacked from other directions, as was shown clearly in the comprehensive discussion of species by Charles Lyell (1797-1875). In his Principles of Geology (vol. II, 1832) he showed the importance that population dynamics and biogeography could have for understanding the nature of species. Although biogeography had received considerable attention,'5 William Kirby ( 1759-1850) and William Spence ( 1783-1860), both prominent and capable entomologists, felt that insect ranges could only be explained as having been "fixed by the will of the Creator." 16 Under their influence, William Swainson asserted in his treatise on animal geography (1835) that the laws of biogeography are forever inscrutable.'7 These men had given up too easily, particularly since good discussions of plant geography had appeared in 1807 and in 1820. The first was by Alexander von Humboldt (1769-1859) and emphasized the effects of inanimate factors (notably climate, topography, and soil) upon plant distribution. He also advocated comparing the distributions of fossil and living species to clarify the means of plant migration and whether species change as climates change.'8 Important though Humboldt's contributions were, of greater 13. Coleman, Georges Cuvier, pp. 131-136. 14. Cuvier, "Discours," p. 41. Eng. trans., p. 77. 15. Nils von Hofsten, "Zur ilteren Geschichte des Diskontinuitiitsproblems in der Biogeographie," Zool. Ann., 7 (1916), 197-353. 16. Kirby and Spence, An Introduction to Entomology, 4 vols. (London: Longman, Hurst, Rees, Orme and Brown, 1815-26; 5th ed., 1828), 1st ed., IV, p. 484. 17. Swainson, A Treatise on the Geography and Classification of Animals (London: Longman, Rees, Orme, Brown, Green and Longman, 1835), pp. 3, 9, 12. 18. Humboldt, Essai sur la giographie des plantes; accompagn6 d'un tableau physique des regions equinoxiales (Paris: Levrault and Schoell, 1807 [dated 1805J; facsimile ed., London: Society for the Bibliography of Natural History, 1959).

230

Studies of Animal Populations from Lamarck to Darwin relevance was the essay by Augustin-Pyramus de Candolle (1778-1841). The understanding of plant geography, de Candolle stated, had been hampered by confusing the concepts of station (habitat) and habitation (range).19 He adopted Linnaeus' classification of stations for plants: maritime or saline; marine; fresh water; damp regions; prairie; cultivated; rocky; sand; sterile soil; rubbish piles; forest; bushes and hedges; subterranean; mountain; parasitic; and saprophytic.20 He discussed the physical factors which influence plant distribution,21 and he went beyond Humboldt by emphasizing the importance of competition: All the plants of a given country, [all those of a given place] are at war one with another. The first which establish themselves by chance in a particular spot, tend, by the mere occupancy of space, to exclude other species-the greater choke the smaller, the longest livers replace those which last for a shorter period, the more prolific gradually make themselves masters of the ground, which species multiplying more slowly would otherwise fill.22 Linnaeus had believed that each species had a definite station in nature which was accompanied by a definite function in the 19. Augustin-Pyramus de Candolle, "G6ographie botanique," Dictionnaire des science naturelles, ed. F. G. Levrault (voL 18, Strasbourg, Paris: Le Normant, 1820), pp. 359-422; see pp. 359, 383. This article was also printed separately as Essai 6l1mentaire de geographie botanique (Strasbourg, Paris, 1820). He had already included definitions of these terms in his Th6orie tle'mentaire de la botanique, ou exposition des principes de la classification naturelle et de l'art de decrire et d'6tudier les veg6taux (Paris; D6terville, 1813), p. 423. 20. De Candolle, "Geog. bot.," pp. 387-390. Carl Linnaeus, Philosophia Botanica in qua Explicantur Fundamenta Botanica cum Definitionibus Partium, Exemplis Terminorum, Observationibus Rariorum, Adjectis Figuris Aeneis (Stockholm: Godofr. Kiesewetter, 1751; several later editions and trans. until 1824), sec. 334, pp. 263-270. This was freely translated by Hugh Rose as The Elements of Botany: Containing the History of the Science . . . (London: T. Cadell, 1775), pp. 368-382. Cf. also the Linnaean dissertation, Stationes Plantarum, Andreas Hedenberg, respondent (Upsala: L. M. Hbjer, 1754); reprinted in Amoenitates Academicae, 4 (1759), 6487. Linnaeus was indebted to Theophrastus, Historia Plantarum, bk. 4. 21. "Geog. bot.," pp. 363-383. 22. "Geog. bot.," p. 384. Trans. Charles Lyell (except that he omitted the bracketed phrase) in Principles of Geology, Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation ([hereafter cited as PG], 3 vols. London: John Murray, 1830-33), II, 131. Cf. Augustin-Pyramus de Candolle, Physiologie vegetal, ou exposition des forces et des fonctions vitales des v.g6taux, pour servir de suit a l'organographie v6g6tale et d'introduction a la botanique gdographique et agricole, 3 vols. (Paris: B6chet jeune, 1832), III, 1401.

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biotic community.23 De Candolle agreed that the structure of the species was correlated with the type of station it occupied, but the reason he gave was no longer prior design for the habitat, but merely that the traits of a particular species enabled it to compete successfully in a particular station. When all environmental factors were considered, he observed, the conditions for the existence of each species would fall within a definite range which might be measured (tolerance of temperature changes for example). Species having small tolerance to changes would live in restricted ranges. No one before de Candolle seems to have stated so clearly the factors involved in plant distribution. His explanation of the ecological effects of competition was especially important for understanding population dynamics.

C. Lyell'sSynthesis De Candolle's contributions to biogeography could be used to clarify both the species question and population biology, and, to an important extent, this achievement was Charles Lyell's. As a foundation for his paleontological conclusions, Lyell discussed, in the second volume of his Principles of Geology, several biological questions related to the species concept: origin, preservation, extinction, hybridity, and succession. These topics were often the contexts for discussions of population. Lyell began by pointing out that, for the paleontologist, it is especially difficult to reach definite conclusions about species because of the time dimension.24 For this reason he reviewed Lamarck's theory of evolution. Lyell disliked the idea of evolution and easily found weaknesses in Lamarck's exposition. Lyell knew that variations exist among the members of a species, but he believed that this was only within fixed limits.25 An exceptionally wide range of variations within some species, 23. Among several discussions of this point, two Linnaean dissertations are especially noteworthy. Specimen academicum de Oeconomia Naturae, I. J. Biberg, respondent (Upsala, 1749); reprinted in Amoen. Acad., 2 (1751), 1-58. Eng. trans. by Benjamin Stllngfleet in Miscellaneous Tracts relating to Natural History, Husbandry, and Physick (London: R. & J. Dodsley, 1759; 4th ed., 1791), pp. 31-108. Dissertatio academia de Politia Naturae, H. Christ. Daniel Wilcke, respondent (Upsala, 1760); reprinted in Amoen. Acad., 6 (1763), 17-39. Eng. trans. by F. J. Brand in Select Dissertations from the Amoenitates Academicae (London: G. Robinson & J. Robson, 1781), pp. 129-166. I have discussed this further in my dissertation, especially p. 176. 24. Lyell, PC, II, 1. William Coleman, "Lyell and the 'Reality' of Species: 1830-1833," Isis, 53 (1962), 325-338. 25. PG, 11, 23.

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Studies of Animal Populations from Lamarck to Darwin and, conversely, close similarities of species within some genera, did not convince him to the contrary: The difference in stature in some races of dogs in comparison to others, is as one to five in linear dimensions, making a difference of a hundred-fold in volume.26 Now there is good reason to believe that species in general are by no means susceptible of existing under a diversity of circumstances, which may give rise to such a disparity in size, and consequently, there will be a multitude of distinct species, of which no two adult individuals can ever depart so widely from a certain standard of dimensions as the mere varieties of certain other species,-the dog for instance. Now we have only to suppose that what is true of size, may also hold in regard to colour and many other attributes.27 The line of thought in this passage could have led to the study of the distribution of traits within a population, but the nature of the species was such a pressing problem that many others passed unnoticed. Having established to his satisfaction the reality of species, Lyell turned to their geographical distribution in order to see "whether the duration of species be limited, or in what manner the state of the animate world is affected by the endless vicissitudes of the inanimate." 28 His whole treatment of this subject can be viewed in terms of population dynamics. The changes in distribution of many animal species is an active response to population pressure, as when immense herds of American bison wander over great distances searching for food: Besides the disposition common to the individuals of every species slowly to extend their range in search of food, in proportion as their numbers augment, a migratory instinct often develops itself in an extraordinary manner, when, after an unusually prolific season, or upon a sudden scarcity of provisions, great multitudes are threatened by famine.29 Since the magnitude of a species' range may affect the size of its population, an understanding of factors affecting geographical distribution is essential for understanding population dynamics. Lyell assembled a good collection of examples to document his thesis that a wide distribution is not evidence of the antiquity of species. The greatest mystery in biogeography was why species are 26. Cuvier, "Discours" (6th ed., Paris, 1830), p. 128 [Lyell's note]. Eng. trans., p. 124. 27. PG, II, 25. 28. PG, II, 66. 29. PG, II, 93-94.

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found where they are but not in similar habitats elsewhere. De Candolle had replied to this question that environmental factors are never exactly the same in different places.30 Lyell realized that there must be more to the answer than this, that part of the explanation lay in the manner of plant and animal dissemination. Climate alone could not explain the peculiar distributions of the floras and faunas of islands. In islands very distant from continents, the total number of plants is comparatively small; but a large proportion of the species are such as occur nowhere else. In so far as the Flora of such islands is not peculiar to them, it contains, in general, species common to the nearest main lands.3' Lyell discussed the information collected by Linnaeus and De Candolle on plant dispersal by wind, ocean currents, animals, and man.32 As his predecessors had, he placed a heavy emphasis on man's role. Man's active transport of species, Lyell stated, was partially counterbalanced by the barriers to migration which man had established through farming and other practices that alter the landscape. He left it up to future ages to determine which factor would prove to be most important. He also examined the factors affecting the distribution of mammals, birds, molluscs, and insects, showing that their movements could be motivated by lack of food, bad weather, overcrowding, and so on. From his close attention to means of dispersal, he postulated a plausible explanation of how mammals living only on mountain tops might occasionally be driven by an adverse environment from one mountain to another. He rejected the suggestion that subterranean conduits might explain how cetacea had migrated from the Mediterranean to the Caspian Sea.33 As a result of the increased knowledge of methods and patterns of distribution of species, theories of a single center of origin like that in Linnaeus' interpretation of Genesis34 were no longer admissible. It seemed most probable to Lyell that species were created in different places and at different times,85 because there were many areas from which species of plants and animals apparently extended their ranges.38 The geological record indicated that species were continually coming into existence and becoming extinct. Lyell accepted neither Lamarck's 30. De Candolle, "Geog. bot.," p. 402. 33. PG, II, 96-99. 32. PG, II, 73ff. 31. PG, II, 70. 34. Linnaeus, Oratio de Telluris habitabilis incremento nelium Haak, 1744); reprinted in Amoen. Acad., 2 (1751), trans., Brand, Dissertations, pp. 71-127. 36. PC, II, 126. 35. PG, II, 123-124.

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Studies of Animal Populations from Lamarck to Darwin belief that fossil species had evolved into the living species nor Cuvier's belief that species were exterminated by periodic geological catastrophes. In his Principles of Geology, he seemed to imply that species were supernaturally created, but at other times he admitted that he hoped to find a more definite answer to this question.37 Conceming extinction, however, he was not ambiguous. Giovanni Battista Brocchi (1772-1826) had thought that a species might have a propensity for aging and that its extinction was thus a physiological necessity.38 Lyell was also seeking regularly operating causes of extinction, but he was inclined to think they were environmental: Brocchi has himself speculated on the share which a change of climate may have had in rendering the Mediterranean unfit for the habitation of certain testacea . . . He must also have been aware that other extrinsic causes, such as the progress of human population, or the increase of some one of the inferior animals, might gradually lead to the extirpation of a particular species, although its fecundity might remain to the last unimpaired.39 Lyell continued by stating that known causes should be investigated before others were introduced (but his position on the creation of species was similar to Brocchi's on their extinction). Lyell had a good appreciation of the significance of competition in nature, citing as evidence the goat-and-dog struggle for existence on Juan Fernandez Island, which Antonio de Ulloa (1716-95) and Joseph Townsend (1739-1816) had described;40 37. Lyeil revealed his further thoughts on the origin of species in the following writings. Letter to J. W. Herschel, June 1, 1836, quoted by Katherine M. Lyell, ed., Life, Letters and Journals of Sir Charles Lyell, Bart, 2 vols. (London: John Murray, 1881), I, 467, 469. "Anniversary Address of the President," Quart. J. Geol. Soc. London, 7 (1851), xxxiilxxi; see p. lxxiii. 38. Brocchi, Conchiologia fossile subapennia, con observazioni geologiche sugli apennini e sul suolo adiacente, 2 vols. (Milan: Stamperia reale, 1814; 2nd ed., 3 vols., Milan: Giovanni Silvestri, 1843), vol. I, chap. 6. 39. PG, II, 129. 40. Ulloa, Relacion historica . . . del viage a la Am&rica meridional, hecho de orden de S. Mag., para medir algunos grados de Meridiano terrestre. . . 5 vols. (Madrid: A. Main, 1748). Eng. trans. by John Adams as A Voyage to South America: Describing at Large the Spanish Cities, Towns, Provinces, &c. on that Extensive Continent. Interspersed throughout with Reflections on the Genius, Customs, Manners, and Trade of the Inhabitants; together with the Natural History of the Country. And an Account of Their Gold and Silver Mines. . . , 2 vols. (London: L. Davis & C. Reymers, 1758; 5th ed., 1807; citation from 3rd ed., 1772), II, bk. 8,

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an article by John Fleming (1785-1857) on animals extirpated in Britain;4'and De Candolle'sdiscussion of competitionamong plant species. Under the influence of Linnaeus, Kirby, and Spence,Lyell stated that insects were especially adaptedfor regulating the growth of plants, because whenever any species of plant became overlyabundant,insects have the power of suddenly multiplying their numbers, to a degree which could only be accomplished in a considerable lapse of time in any of the larger animals, and then [after eating the plants] as instantaneously relapsing, without the intervention of any violent disturbing cause, into their former insignificance . . . no sooner has the destroying commis-

sion been executed, than the gigantic power becomes dormant.42

Adverse changes in the weather, he noted, often decimated these insects. This view of insects as a regulatory agent in nature was, however, inconsistent with the account immediately following. In vivid detail he summarized accounts of the devastations which had been caused by plagues of aphids, ants, caterpillars, He thus paradoxically attributed to insects the and locusts.43 dual roles of both preserving and disrupting the balance of nature. Alfred Russel Wallace (1823-1913) noticed this discrepancyin Lyell'sargument: Some species exclude all others in particulartracts. Where is the balance? When the locust devastates vast regions and

causes the death of animals and man, what is the meaning of saying the balance is preserved? [Are] the Sugar Ants in the West Indies [as well as] the locusts which Mr. Lyell says have destroyed800,000 men an instance of the balance of species? To human apprehensionthere is no balance but a struggle in which one often exterminates another.44 chap. 4, p. 220. Joseph Townsend, A Dissertation on the Poor Laws (London: 1786; citation from n. ed., 1817), pp. 44-45. 41. Fleming, "Remarks Illustrative of the Influence of Society on the Distribution of British Animals," Edinburgh Phil. J., 11 (1824), 287-305. 42. PG, II, 134. 43. PG, II, 136-138. Among the sources which Lyell cited was the important paper by William Curtis, "Observations on Aphids, chiefly intended to show that they are the principal cause of Blights in Plants, and the sole cause of the Honey-Dew," Trans. Linn. Soc. London, 6 (1802), 75-94. For a discussion of earlier observations on the population biology of aphids, see pp. 16-17 of my article on "Leeuwenhoek as a Founder of Animal Demography," J. Hist. Biol., 1 (1968), 1-22. 44. Wallace, "Species Notebook," pp. 49-50. This notebook, which was written between 1854 and 1859, is being prepared for publication by Dr.

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Studies of Animal Populations from Lamarck to Darwin The factors which tend to preserve the balance of nature received Lyell's close attention. He described a buffering effect which allows stress in one part of nature to be dissipated to some extent by reactions in other parts. His analysis of this effect was mainly concerned with predation. Although it may usually be remarked that the extraordinary increase of some one species is immediately followed and checked by the multiplication of another, yet this is not always the case, partly because many species feed in common on the same kinds of food, and partly because many kinds of food are often consumed indifferently by one and the same species. In the former case, where a variety of different animals have precisely the same taste, as for example, when many insectivorous birds and reptiles devour alike some particular fly or beetle, the unusual numbers of the latter may only cause a slight and almost imperceptible augmentation of each of those species of bird and reptile. In the other instance, where one animal preys on others of almost every class, as for example, where our English buzzards devour not only small quadrupeds, as rabbits and fieldmice, but also birds, frogs, lizards, and insects, the profusion of any one of these last may cause all such general feeders to subsist more exclusively upon the species thus in excess, and the balance may thus be restored.45 Sometimes, he continued, this equilibrium is maintained by an interaction between species inhabiting different kinds of environments, as when amphibious animals eat either aquatic or terrestrial food, depending upon which is more abundant. The fish which migrate from the ocean into rivers even provide a link between the animals inhabiting the land and those of the deep seas. After this excellent digression into the interactions between species, Lyell returned to his earlier discussion of species distribution in time and space in order to apply his conclusions. He had shown some of the ways in which the station of each species depends upon both its living and nonliving environment. To demonstrate that species were exterminated fairly frequently, he needed only to show further that the living and nonH. Lewis McKinney. The above quotation is taken from McKinney, "Alfred Russel Wallace and the Discovery of Natural Selection," Journal of the History of Medicine and Allied Sciences, 21 (1966), 333-357; see pp. 345346. The references to which Wallace referred Lyell had obtained mainly from Kirby and Spence, Entomology, I, 183-215. The interesting article on sugar ants was by John Castles, "Observations on the Sugar Ants," Phil. Trans. Roy. Soc. London, 80 (1790), 346-358. 45. PG, II, 138-139.

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living factors in the environment undergo steady changes which can alter a habitat enough to eliminate the species occupying it. The crucial factor would often be the increase of some population: when any region is stocked with as great a variety of animals and plants as the productive powers of that region will enable it to support, the addition of any new species, or the permanent numerical increase of one previously established, must always be attended either by the local extermination or the numerical decrease of some other species.46 As an illustration he suggested an enclosed park stocked with all the deer it could support. One could not add sheep without removing some of the deer. His point is clear, though the illustration was not well chosen: since deer browse and sheep graze, they do not compete closely for food. The invasion of a new species into a region, he realized, would probably affect directly or indirectly almost all the species already there. His hypothetical example in this case was a good illustration of interrelationships and was not susceptible to the complaint of inaccuracy. Polar bears occasionally had been reported to have floated over on ice from Greenland to Iceland. Speculating upon the effect it would produce if they became permanently established on the latter island, Lyell observed: The [populations of] deer, foxes, seals, and even birds, on which these animals sometimes prey, would be soon thinned down. But this would be a part only, and probably an insignificant portion, of the aggregate amount of change brought about by the new invader. The plants on which the deer fed being less consumed in consequence of the lessened numbers of the herbivorous species, would supply more food to several insects, and probably to some terrestrial testacea, so that the latter would gain ground. The increase of these would furnish other insects and birds with food, so that the numbers of these last would be augmented. The diminution of the seals would afford a respite to some fish which they had persecuted; and these fish, in their turn, would then multiply and press upon their peculiar prey. Many waterfowls, the eggs and young of which are devoured by foxes, would increase when the foxes were thinned down by the bears; and the fish on which the water-fowls subsisted would then, in their tum, be less numerous. Thus the numerical 46. PG, II, 142.

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Studies of Animal Populations from Lamarck to Darwin proportions of a great number of the inhabitants, both of the land and sea, might be permanently altered by the settling of one new species in the region; and the changes caused indirectly might ramify through all classes of the living creation, and be almost endless.47 The traditional emphasis upon the interdependence of the links in the "great chain of being" probably influenced Lyell when he emphasized the vast interdependence of species. However, the reality of extinction prevented an excessive emphasis upon interdependence. He noted that slight changes in climate or topography might eliminate a species from a region and cause a readjustment in the populations. Whatever the altered factor, a new equilibrium would eventually be reached, but one or more species might be eliminated in the process. Lyell realized that man has become an important factor in the alteration, and sometimes obliteration, of natural areas. He also noticed that where man has replaced a natural area with an agricultural crop, the productivity of the land has often decreased.48 There were animals like the dodo which had been exterminated by hunting,49 but as Fleming had observed,50 when fanning practices eliminated the habitat of a species, that species also disappeared. Besides these direct actions of man, he had introduced into foreign lands domestic animals which had also reduced the population of native species. In less than three centuries the few horses and cattle which had been brought to the pampas of Buenos Aires had increased to over fifteen million, and the population of native species must have been reduced as a consequence. Goats and dogs had overrun Juan Fernandez Island.51 Lyell expected the human population to increase continually, especially in America and Australia, and he predicted that other species would be continually exterminated as a consequence. He disagreed with those who lamented this, because the spread of any other species would produce the same effect.62 He did not discuss the desirability of preserving threatened species for scientific or esthetic reasons. In concluding his discussion of species, Lyell speculated upon the probable rate of their extinction and replacement.53 Since there seemed to exist over a million species of plants and animals, more than a million years would be needed if one were exterminated and one created each year. At that rate, only one species from Europe would be replaced in twenty 47. PC, II, 143-144. 48. PG, II, 147-148. 49. PG, II, 150-151. 50. Fleming, "Remarks," p. 291. 51. PG, II, 154. 52. PG, II, 156. 53. See above, note 37.

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years, and 8000 years might go by before a new species of mammal was replacedin Europe.He thereforewas not disturbed that no new species had been noticed in Europe within historical time.54

Lyell did not introduce any new concepts into population studies, but he made a synthesis which, though not as comprehensive as that of Sir Matthew Hale (1609-76),55 nevertheless ranks with his seventeenth-centurypredecessor'sin importance. No one before Lyell had expressed as clearly as he did the fluidity of populations. His account shows populations expanding or contracting in response to a variety of factors, the intensity of which varies randomly. He placed much less emphasis upon the intrinsic physiological control of population which had seemed important to Buffon, Lamarck, and Brocchi. On the other hand, although influenced by Linnaeus' concept of the economy of nature, he did not overemphasize it. Competition and the extinction of species were also important for Lyell's synthesis. D. Forbes,Biogeography,and the CommunityConcept Another British scientist with competence in both geology and biology, who continued to develop some of the ecological concepts which Lyell had discussed, was EdwardForbes (181554). Biogeographyfascinated him, and he spent much of his time engaged in field studies. In 1841-42 he made extensive dredgings in the Aegean Sea and concluded that species were restricted to definite habitats, which could be defined in terms of depth, substrate,currents, temperature,and so forth. He distinguished eight zones, each having characteristic species, but did not describe these zones as having permanent assemblages of species. Forbes described in concrete detail the dynamic aspects of biotic communities which De Candolle and Lyell had described hypothetically. In 1843, he reported that: The eight regions in depth are the scene of incessant change. The death of the individuals of the several species inhabiting them, the continual accession, deposition and sometimes washing away of sediment and coarser deposits, the action of the secondary influences and the changes of elevation which appear to be periodically taking place in the eastern Mediterranean,are ever modifying their charac54. PG, II, 181-182. 55. Hale, The Primitive Origination of Mankind, Considered and Examined According to the Light of Nature (London: William Shrowsbery, 1677), pp. 203-238. I have discussed this work in my dissertation, chap. 2.

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Studies of Animal Populations from Lamarck to Darwin ter. As each region shallows or deepens, its animal inhabitants must vary in specific associations, for the depression which may cause one species to dwindle away and die will cause another to multiply. The animals themselves, too, by their over-multiplication, appear to be the cause of their own specific destruction. As the influence of the nature of sea-bottom determines in a great measure the species present on that bottom, the multiplication of individuals dependent on the rapid reproduction of successive generations of Mollusca, &c. will of itself change the ground and render it unfit for the continuation of life in that locality until a new layer of sedimentary matter, uncharged with living organic contents, deposited on the bed formed by the exuviae of the exhausted species, forms a fresh soil for similar or other animals to thrive, attain their maximum, and from the same cause die off. This, I have reason to believe, is the case, from my observations in the British as well as the Mediterranean seas.56 Although Linnaeus had described how the growth of some species could prepare the way for the invasion of others,57 no one before Forbes seems to have emphasized how inevitable this often is. In his 1843 paper and in another published the following year,58 Forbes came close to the modern conception of the biotic community which was first explicitly formulated by Karl August Mobius (1825-1908) in 1877 in a study on oysters.59 Forbes's research on the distribution of species enabled him to generalize about their geographical as well as ecological distribution. Richard Owen (1804-92) had discredited Cuvier's assumption that all terrestrial species in an area become extinct nearly simultaneously.00 Owen's conclusion strengthened Lyell's hypothesis that changes in the distribution of species 56. Forbes, "Report on the Molluscs and Radiata of the Aegean Sea, and on Their Distribution, Considered as Bearing on Geology," Rep. Brit. Assoc. Advan. Sci., 13 (1843), 130-193; quotation, p. 173. 57. Linnaeus, "Oeconomy," pp. 78-79. 58. Forbes, "On the Light Thrown on Geology by Submarine Researches; being the Substance of a Communication Made to the Royal Institution of Great Britain, Friday Evening, the 23d February 1844," Edinburgh Phil. J., 36 (1844), 318-327. 59. M8bius, Die Auster und die Austernwirthschaft (Berlin: 1877). Eng. trans. by H. J. Rice as "The Oyster and Oyster-Culture," in U.S. Commission of Fish and Fisheries Report for 1880 (Senate Miscellaneous Document 29 of 46th Congress, 3rd Session), pp. 683-751; see p. 721. 60. Owen, "Report on the British Fossil Mammalia," British Association Report 12 (1842), 54-74; 13 (1843), 208-241. Owen, A History of British Fossil Mammals and Birds (London: John Van Voorst, 1846), p. xxxi.

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occur gradually, as do changes in the topography of land. Forbes's investigations were also consistent with this view. From a study of the past and present fauna and flora of the British Isles, he concluded that its species had arrived there neither by special creation nor by active transport by man, but by migration over a past land bridge which had sunk beneath the sea.6' Before tuming to Darwin, it is appropriate to mention the philosopher Herbert Spencer (1820-1903), because in 1852 he published a theory of population62 which Darwin may have read. Spencer, however, cannot be considered as having made a significant contribution to the development of Darwin's ideas on population. Spencer offered physiological explanations, but Darwin, like Lyell, was eventually to choose an ecological approach to population biology. Therefore, though Spencer's paper falls within the period under discussion, his ideas are beyond the scope of this paper.63 II. THE DEVELOPMENT OF DARWIN'S IDEAS ON POPULATION The theoretical advances which have been described thus far show that the importance of population pressure in the living world was becoming increasingly clear. Yet even Lyell's capable synthesis of paleontology and biology had not achieved an adequate understanding of population dynamics. Had Lyell accepted Lamarck's ideas on evolution, however, he might not have achieved as good an understanding as he did, because Lamarck's emphasis upon adaptation obscured the importance of population pressure, competition, and natural selection. The effects of population pressure in nature became an important aspect of the theory of evolution by natural selection of Charles Darwin (1809-82), and the revolution in biology which he initiated had a profound effect upon the understanding of population biology. When he embarked on the voyage of the Beagle in December 1831, Darwin took with him the first volume of Lyell's Princi61. Forbes, "On the Connexion between the Distribution of the Existing Fauna and Flora of the British Isles and the Geological Changes which Have Affected Their Area," Memoirs of the Geological Survey (of Great Britain), 1 (1846), 336-432; see p. 337. 62. Spencer, "A Theory of Population deduced from the General Law of Animal Fertility," Westminster Rev., 57 (April 1852), 468-501. This essay was later expanded in his Principles of Biology, 2 vols. (London: Williams and Norgate, 1864-67; 2nd ed., 1898-99), pt. 6. 63. Spencer is, however, discussed in my dissertation, chap. 4.

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Studies of Animal Populations from Lamarck to Darwin ples of Geology.64 He received the newly published second volume at Monte Video in November 1832.65 Both the contents and methods of Lyell's science were mastered by Darwin. He saw first-hand the vast herds of horses and cattle on the Patagonian pampas which Lyell had discussed, and Darwin reported in The Voyage of the Beagle the great devastations which droughts and other environmental factors caused periodically to their populations.66f His own scientific observations impressed upon Darwin the importance of population dynamics; it is therefore not surprising that he was later to recognize this factor as the key to his theory of natural selection. Darwin did not publish anything concerning population in the two decades between The Voyage of the Beagle and The Origin of Species. Since the latter book is a major landmark in the history of population studies, it is fortunate that he left records and reminiscences about his thoughts during this period-letters, notebooks, a journal, an autobiography, and three drafts of the Origin.f17 From these sources one can gain 64. Darwin wrote that "this book was of the highest service to me in many ways. The very first place which I examined, namely St. Jago in the Cape Verde islands, showed me clearly the wonderful superiority of Lyell's manner of treating geology, compared with that of any other author, whose works I had with me or ever afterwards read." The Autobiography of Charles Darwin, 1809-1882, with Original Omissions Restored, ed. Nora Barlow (New York: Harcourt, Brace, 1959), p. 77. 65. Darwin's copy of Lyell's Principles has been preserved. The second volume is not annotated very much. Sydney Smith, "Evolution: Two Books and Some Darwin Marginalia," Victorian Studies, 3 (1959), 109-114; see pp. 112-113. 66. Darwin, Journal of Researches into the Geology and Natural History of the Various Countries Visited by H.M.S. Beagle, under the Command of Captain Fitzroy, R.N., from 1832 to 1836 (London: Henry Colburn, 1839; citation from facsimile ed., New York: Hafner, 1952), chap. 7, pp. 155158; chap. 9, pp. 211-212. 67. A bibliography of most of the published Darwin letters has been included by Gavin de Beer in "Some Unpublished Letters of Charles Darwin," Notes and Records Roy. Soc. London, 14 (1959), 12-66. More recently, Nora Barlow has edited Darwin and Henslow: The Growth of an Idea; Letters 1831-1860 (Berkeley: University of California Press, 1967). Gavin de Beer, ed., "Darwin's Journal," Bull. Brit. Museum (Nat. Hist.) Hist. Ser., 2 (1959), 3-21. De Beer, "Darwin's Notebooks on Transmutation of Species. Part I. First Notebook (July 1837-February 1838)," ibid., 2 (1960), 25-73; "Part II. Second Notebook (February to July 1838)," ibid., 2 (1960), 77-117; "Part III. Third Notebook (July 15th 1838-October 2nd 1838)," ibid., 2 (1960), 121-150; "Part IV. Fourth Notebook (October 1838-10 July 1839)," ibid., 2 (1960), 153-183; De Beer and M. J. Rowlands, eds., "Addenda and Corrigenda," ibid., 2 (1961), 187-200; De Beer, M. J. Rowlands, and B. M. Skramovsky, eds., "Part VI. Pages Excised by Darwin," ibid., 3 (1967), 131-176. Paul H. Barrett, ed., "A Transcription of Darwin's First Notebook on 'Transmutation of Species,"' Bull. Museum

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an insight into his scientific methods, his debts to other scientists, and the pathways he followed from his early gropings to the form in which his ideas finally appeared in print.68 Lyell's treatment of biogeography had been both comprehensive and incisive, but it lacked the evolutionarydimension. Darwin soon realized that a major gap existed in the understanding of this subject, and it was mainly the desire to explain his own biogeographicalobservationsthat compelled him to accept the idea of evolution.69His evolutionarytheory could explain better than any other why island species resembled, but were not always identical to, mainland species. He conducted experiments to determine the viability of seeds that had been soaked in sea-water to support his belief that seeds had often been disseminated by ocean currents.70Darwin realized that the mountain-topproblem, which Lyell had solved hypothetically, could be easily explained by assuming that species which were adjusted to cold climates had retreated up mountains as the Ice Age had ended.7' This explanation had occurred also to Forbes, who published it in 1846.72With his broader knowledge of means of dispersal, Darwin rejected Forbes's hypothesis of oceanic land bridges73as unnecessary Comp. Zool. Harvard University, 122 (1960), 245-296. Darwin's Autobiography is cited above, note 64. The first two drafts of his Origin were published by Francis Darwin in The Foundations of the Origin of Species: Two Essays Written in 1842 and 1844 (Cambridge, Eng.: Cambridge University Press, 1909). These drafts were reprinted by Gavin de Beer in Evolution by Natural Selection (Cambridge, Eng.: Cambridge University Press, 1958). The third draft has not been published, but it has been described by Robert C. Stauffer, "'On the Origin of Species:' an Unpublished Version," Science, 130 (1959), 1149-1152. 68. From the evolutionary point of view, this has already been done. Cf. Sydney Smith, "The Origin of 'The Origin,"' The Advancement of Science, 16 (1960), 391-401. Gavin de Beer, "The Origins of Darwin's Ideas on Evolution and Natural Selection," Proceedings of the Royal Society of London, 155 1B] (1961), 321-338. 69. Darwin, Autobiography, p. 118. 70. Darwin, "On the Action of Sea-water on the Germination of Seeds," Linnean Society Journal (Botany), 1 (1857), 130-140; "Does Sea-water Kill Seeds?" The Gardener's Chronicle, (26 May 1855), 356-357; "Vitality of Seeds," ibid., (17 Nov. 1855), 758; "Effect of Salt-water on the Germination of Seeds," ibid., (24 Nov. 1855), 773. Darwin discussed these in letters experiments with Professor John Stevens Henslow (1796-1861) dated 2, 7, 11, 14, and 21 July 1855, 10 November 1855, and 3 January 1856. Darwin and Henslow, pp. 176-183, 188, 191. 71. Darwin, Autobiography, pp. 124-125; Notebook II, MS, p. 184; printed in "Notebooks," VI, 150; Evolution, p. 67. 72. Forbes, "Fauna and Flora," pp. 343-346. 73. Ibid., pp. 348-352. Cf. letter from Forbes to Darwin, [Feb.], 1846. More Letters of Charles Darwin. A Record of His Work in a Series of Hitherto Unpublished Letters, ed. Francis Darwin and A. C. Seward, 2 vols. (London and New York: D. Appleton, 1903), I, letter 20.

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Studies of Animal Populationsfrom Lamarckto Darwin to account for island life.74 Darwin's conclusions in biogeography were indirectly very important for population theory, but a more direct relationship might have developed had he or someone else done research on the population dynamics of mountain-topor island species. Extinction was another subject that Lyell had handled very well theoretically. A hypothetical argument, however, is not scientific proof. In his first notebooks on evolution, written in 1837 and 1838, Darwin recordedhis search for a physiological cause for extinction. He thought that extinction must be part of the evolutionaryprocess: ?Law: existence definite without change, superinduced, or new species. Therefore animals would perish if there was nothing in countryto superinducea change? Seeing animals die out in S. America with no change, agrees with belief that Siberian animals lived in cold countries and thereforenot killedby cold countries.75

He was then consciously opposed to Lyell's explanation of extinction as being caused only by competition and environmental changes: It is a wonderful fact-Horse, Elephant and Mastodon dying out about the same time in such different quarters. -Will Mr. Lyell say that some circumstance killed it [them] over a tract from Spain to S. America?-(Never). They die, without they change, like golden Pippins; it is a generation of species like generation of individuals.

Why does individual die? To perpetuate certain peculiarities (therefore adaptation), and to obliterate accidental varieties, and to accommodate itself to change (for, of course change even in varieties is accommodation). Now this argument applies to species.-If individual cannot procreate he has no issue; so with species. -76 74. Darwin, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (London: John Murray, 1859; facsimile ed., Cambridge, Mass.: Harvard University Press, 1964), p. 357. Darwin's letters on biogeography are in More Letters, American ed., chaps. 6-7. Ernst Mayr, "Isolation as an Evolutionary Factor," Proc. Am. Phil. Soc., 103 (1959), 221-230. Philip J. Darlington, Jr., "Darwin and Zoogeography," ibid., 307-319. Hofsten, "Diskontinuitatsproblems," pp. 321-329 et passim. 75. Darwin, Notebook I, MS, pp. 61-62. Cf. Notebook I, MS, p. 153: "There is no more wonder in extinction of individuals than of species." Printed in "Notebooks," VI, 135. I wish to thank Lady Nora Barlow, Mr. George P. Darwin, and Mr. H. R. Creswick of the Cambridge University Library for granting me permission to quote from the writings of Charles Darwin. 76. Darwin, Notebook I, MS, pp. 63-64.

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This line of thought persisted into the fourth notebook,77 but by the time he wrote the second notebook he had already begun to collect evidence of extinction being caused by extrinsic factors: "Epidemics of South Sea wonderful case of extermination of species.-Epidemic amongst trees. Plane trees all died certain year." 78 When he began his fourth notebook, in October 1838, he was very close to Lyell's point of view. On the one hand, he had decided that environmental changes are important factors,79 and on the other, having just read Malthus, he realized that competition must also be an important cause of extinction.80 When he published The Origin of Species Darwin still emphasized that extinction was not well understood, but that the only factors that were known to cause it were environmental changes and competition.81 Darwin's reading of Malthus convinced him that De Candolle and Lyell had been right in emphasizing the importance of competition: 28th [September, 1838] we ought to be far from wondering of changes in numbers of species, from small changes in nature of locality. Even the energetic language of Decandolle does not convey the warring of the species as inference from Malthus. -increase of brutes must be prevented solely by positive checks, excepting that famine may stop desire. -in nature production does not increase, whilst no check prevail, but the positive check of famine & consequently death. I do not doubt every one till he thinks deeply has assumed that increase of animals exactly proportionate to the number that can live.Population is increase at geometrical ratio in FAR SHORTER time than 25 years-yet until the one sentence of Malthus no one clearly perceived the great check amongst men.-there is spring, like food used for other purposes as wheat for making brandy. -Even a few years plenty, makes population in man increase & an ordinary crop causes a dearth. take Europe on an average every species must have same number killed year with year by hawks, one species of hawk decreasing in numby cold &c. -ven ber must affect instantaneously all the rest. -The final cause of all this wedging, must be to sort out proper structure, & adapt it to changes. -to do that for form, which 77. Ibid. II, MS, p. 234; Ibid. III, MS, p. 72; Ibid. IV, MS, p. 43. 78. Ibid. II, MS, p. 64. 79. Ibid. IV, MS, p. 48. 80. Ibid. IV, MS, p. 3. He had read the 6th ed. of Malthus, Essay on the Principle of Population (1826). 81. Darwin, Origin, 1st ed., pp. 109-110, 317-322.

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Studies of Animal Populations from Lamarck to Darwin Malthus shows is the final effect (by means however of volition) of this populousness on the energy of man. One may say there is a force like a hundred thousand wedges trying [to] force every kind of adapted structure into the gaps in the economy of nature, or rather forming gaps by thrusting out weaker ones.82 Darwin had been aware of both population fluctuations and the struggle for existence. However, he had been seeking, perhaps under the influence of his grandfather, Erasmus Darwin, and of Lamarck, intrinsic causes of evolution. Now he realized that intrinsic variations alone could not account for evolution. In his fourth notebook, perhaps to emphasize to himself that he had improved upon Lyell's synthesis, he wrote: "Extinction & transmutation, two foundations, hitherto confounded, of geology." 83 Having achieved the main points of his theory, Darwin began the large task of evaluating each of the factors in detail. Shortly after reading Malthus he realized that, because of variation and population pressure, there would be a tendency for organisms to live in every possible situation. This was an important realization for the history of ecology as well as for evolutionary theory, because thereafter Darwin searched for the ways that different roles can lead different populations of a species into reproductive isolation. This question reinforced Darwin's interest in ecology. Therefore, his early statements on ecological diversity and evolution are important for indicating the channel within which the mainstream of his future ecological thoughts would flow. In his first notebook he pondered the significance of the interdependence of species: There must be progressive development; for instance none ? of the vertebrata could exist without plants & insects had been created; but on other hand creations; of small animals must have gone on since from parasitical nature of insects & worms. -In abstract we may say that vegetables & most of insects could live without animals.84 In his second notebook he speculated further: The quantity of life on planet at different periods depends on relations of desert, open ocean, &c. This probably on long 82. Darwin, Notebook III, MS, pp. 134-135; printed in "Notebooks," VI, 162-163. Cf. Darwin, Autobiography, p. 120. Wallace also got the idea of evolution by natural selection after reading Lyell and Malthus. McKinney, "Wallace," pp. 354-356. 83. Notebook IV, MS, p. 87; printed in "Notebooks," VI, 170. 84. Notebook I, MS, p. 108; printed in "Notebooks," VI, 134.

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average equal quantity, 20 on relation of heat & cold, therefore probablyfewer now than formerly. The number of forms depends on the extemal relations (a fixed quantity) & on subdivision of stations & diversity, this perhaps on long average equal.85 These statements were rather vague and unsubstantiated,but they show that Darwin did not have the skeptical reaction that Wallace did to Lyell's discussion of the balance of nature. In his fourth notebook, Darwin had already achieved a greater subtlety in explaining how ecological diversity and population pressurecontributedto his theory: The enormous number of anIimals in the world depends on their varied structure & complexity.-hence as the forms became complicated, they opened fresh means of adding to their complexity.-but yet there is no necessary tendency in the simple animals to become complicated although all perhaps will have done so from the new relations caused by the advancimgcomplexityof others... The geologico-geographicochanges must tend sometimes to augment & sometimes to simplify structures. Without enormous complexity, it is impossible to cover whole surface of world with life . . . it would not be possible to simplify the organization of the different beings . . . without reducing

the number of living beings-but there is the strongest possible [tendency?] to increase them, hence the degree of developmentis either stationaryor more probablyincreases.86 By 1842 Darwin felt that his conception of evolution had become coherent enough to be expressed in a first sketch, which contained a few suggestive but undeveloped ideas on population dynamics. A section entitled "Natural selection" examined the implications for his theory of De Candolle'sdiscussion of the "war of nature"87 and the Malthusian principle that population tends to increase faster than subsistence. He felt the need for definite data on population biology, for he wrote such notes to himself as "calculate robins-oscillating 85. Notebook II, MS, p. 147; printed in "Notebooks," VI, 149. 86. Notebook IV, MS, pp. 95-97. Darwin's ecological ideas have been discussed by the following. Robert C. Stauffer, "Ecology in the Long Manuscript Version of Darwin's Origin of Species and Linnaeus' Oeconomy of Nature," Proc. Am. Philos. Soc., 104 (1960), 235-241. Peter Vorzimmer, "Darwin's Ecology and Its Influence upon His Theory," Isis, 56 (1965), 148-155. Kazuo Sibuya, 'Present-day Evaluation of the Ecological Aspects of Darwin's Theories in Japan," Japanese Studies in the History of Science, 1 (1962), 117-124. 87. Darwin, Evolution, pp. 46-47.

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Studies of Animal Populations from Lamarck to Darwin from years of destruction." 88 He suspected that the checks to the population of most species fell on the eggs and young, but he wanted proof. His discussion of "Geographical Distribution" in the sketch was limited to explaining how it contributed to his theory. Since there was little documentation, he was not yet drawing much upon his own observations for evidence. One sentence which discussed continental movements and extinction perhaps indicates an influence of Cuvier: "as continent (most extinction during formation of continent) is formed after repeated elevation and depression, and interchange of species we might foretell much extinction . ." 89 In 1844 Darwin was able to write a longer essay on his ideas. As an indication of the extent to which his ideas had fallen into place, and also as evidence of the central role of population biology for his theory, one should notice that the section of this essay entitled "Natural Means of Selection" was to be printed in 1858, along with Wallace's paper, as part of the first public announcement of the theory of evolution by means of natural selection.90 In the intervening time between the first sketch and this essay, Darwin had collected more facts and arguments. His thesis was that more offspring are produced than the area in which they live can support, that those which are best adapted to the environment are the ones which live to perpetuate the species, and that since the environment undergoes constant changes the traits which enable a species to survive will alter correspondingly, resulting in the survival of those individuals modified to fit best into the new environment. The first of these points would seem to require little documentation. High reproductive potentials in many plants and animals were well known, and he had only to remind his readers that "many practical illustrations of this rapid tendency to increase are on record." 91 He cited Malthus' statement that man, a slow breeder, could double his numbers in twenty-five years when subsistence permitted. Since Malthus' famous statement had been attacked as being unreliable,92 one might 88. Ibid. 89. Ibid., p. 71. 90. Darwin, Essay of 1844, in Evolution, pp. 91-254; see pp. 116-121. Darwin and Wallace, "On the Tendency of Species to Form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection," J. Linn. Soc. (Zool.), 3 (1859), 45-62; reprinted in Evolution, pp. 257-279. 91. Evolution, pp. 117, 260. 92. Michael Thomas Sadler, The Law of Population: A Treatise, in Six Books; in Disproof of the Superfecundity of Human Beings, and Developing the Real Principle of Their Increase, 2 vols. (London: J. Murray, 1830),

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wonder why Darwin cited it rather than strictly biological data. The difficulty was that although there were numerous records of the number of offspring which organisms could produce at the breeding season, there were virtually no data on the increase of wild populations of a species over more than one generation. Consequently, Darwin, like several predecessors,93 calculated the hypothetical increase of a population, assuming no mortality: Suppose in a certain spot there are eight pairs of [robins] birds, and that only four pairs of them annually (including double hatches) rear only four young; and that these go on rearing their young at the same rate: then at the end of seven years (a short life, excluding violent deaths, for any birds) there will be 2048 robins, instead of the original sixteen; as this increase is quite impossible, so we must conclude either that robins do not rear nearly half their young or that the average life of a robin when reared is from accident not nearly seven years. Both checks probably concur. The same kind of calculation applied to all vegetables and animals produces results either more or less striking, but in scarcely a single instance less striking than in man.94 Darwin's hypothetical rate of increase in the above example was, not surprisingly, the same geometrical rate which Malthus had suggested could apply to man. The reproductive potential of any songbird was certainly great, but casual observation would satisfy anyone that their numbers in any neighborhood remained fairly static from year to year. Unfortunately, he still did not know precisely why this was true: In the majority of cases it is most difficult to imagine where the check falls, generally no doubt on the seeds, eggs, and young; but when we remember how impossible even in mankind (so much better known than any other anixnal) it is to infer from repeated casual observations what the average of life is, or to discover how different the percentage of deaths to the births in different countries, we ought to feel no legitimate surprise at not seeing where the check falls in animals and plants. It should always be remembered that in most cases the checks are yearly recurrent in a small regular degree, and in an extreme degree during occavol. 1, bk. 2; vol. 2, bk. 3. Kenneth Smith, The Malthusian Controversy (London: Routledge & Kegan Paul, 1951), pp. 194-195. 93. See my article on "Leeuwenhoek as a Founder of Animal Demography" and my dissertation, chaps. 2-3. 94. Evolution, pp. 117, 259-260.

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Studies of Animal Populations from Lamarck to Darwin sionally unusually cold, hot, dry, or wet years, according to the constitution of the being in question. Lighten any check in the smallest degree, and the geometrical power of increase in every organism will instantly increase the average numbers of the favoured species.95 However, he had found in South America a convincing example of the effects which weather has on the population of species: During the years 1826 to 1828, in La Plata, when from drought, some millions of cattle perished, the whole country swarmed with innumerable mice: now I think it cannot be doubted that during the breeding season all the mice (with the exception of a few males or females in excess)96 ordinarily pair; and therefore that this astounding increase during three years must be attributed to a greater than usual number surviving the first year, and then breeding, and so on, till the third year, when their numbers were brought down to their usual limits on the return of wet weather.97 In another section of the 1844 essay, entitled "Extinction of Species," Darwin suggested that species do not die out suddenly in gigantic catastrophes; rather, they graduaUly become rarer and rarer until they disappear altogether. This, he thought, would be caused by the increasing severity of one or more unfavorable environmental factors. For example: In the Falkland Islands the check to the increase of the wild horse is said to be loss of the suckling foals, from the stallions compelling the mares to travel across bogs and rocks in search of food: if the pasture on these islands decreased a little, the horse, perhaps, would cease to exist in a wild state, not from the absolute want of food, but from the impatience of the stallions urging the mares to travel whilst the foals were too young.98 Darwin's statement, written in 1842, that little was known of the relative importance of factors limiting populations, was 95. Ibid., pp. 118, 260. 96. Darwin had made a note in Notebook III, MS, p. 152 (printed in "Notebooks," VI, 164) that he thought Adolphe Quetelet (1796-1874) mentioned facts "about proportion of sexes, at birth & causes" in "On Man and the Development of his Faculties, &c." Athenaeum, nos. 406, 407, 409 (1835), 593-595, 611-613, 658-661. Quetelet wrote on p. 611: "an examination of births registered in France during a lapse of fourteen years, [showed] that the average number of male births to female was 106.38 to 100 . . . the number of male births is relatively less predominant in cities than in agricultural districts." 98. Ibid., p. 167. 97. Evolution, pp. 117, 260.

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excessively modest when he published it in 1858. On March 3, 1857, he had completed the fifth chapter of the third draft of the Origin. In that chapter he discussed limiting factors under several headings: "Checks to increase in animals," "Mutual checks of animals & plants," "On the struggle between plant & plant,"and "Factsapparentlyopposed to there being a severe struggle in all nature."99 The phrase "strugglefor existence," which was to attract so much attention and cause misunderstandings in the public mind, was carefully defined in all shades of meaning, including competition, predation, struggle against physical factors (cold, drought,etc.), and the productionof the greatest number of viable offspring. He carefully considered his terminology: In many of these cases, the term used by Sir C. Lyell of "equilibriumin the number of species" is the more correct but to my mind it expresses far too much quiescence. Hence I shall employ the word struggle, which has been used by Herbert & Hooker &c., including in this term several ideas primarilydistinct, but graduatinginto each other.'00 Among animals, Darwin observed that the direct competition of individuals, which "strugglefor existence" was later taken to mean, is greatest among varieties of the same species,'01 similar species, or dissimilar species with the same habits. His example of the last was the competition which might occur between cattle and locusts for the same food. He discussed many examples of competition between similar species, such as the replacement of the Black Rat by the Norway Rat in all parts of the worldwhere man has accidentallyintroducedboth.102 Plants compete directly for physical requirements, such as light, water, and space. The species native to an area would most likely be the best adapted to obtain these requirements in that area, which would explain why introduced species 99. This became the third chapter in the published version of the Origin. I am indebted to Professor Robert C. Stauffer for making available to me a typescript of this chapter from Darwin's long version of the Origin [hereafter cited as LVO]. 100. LVO, fol. 30B. Lyell, PC, II, 134 (page heading). William Herbert "Local Habitations and Wants of Plants," Journal of the (1778-1847), Horticultural Society, 1 (1846), 44-59; see p. 47. Joseph Dalton Hooker Flora Indica: Being a Systematic and Thomas Thomson (1817-1911), Account of the Plants of British India, together with Observations on the Structure and Affinities of Their Natural Orders and Genera (London: W. Pamplin, 1855), pp. 41-42. 101. Cf. Darwin, Notebook II, MS, p. 125. Cf. Garrett Hardin, "The Competitive Exclusion Principle," Science, 131 (1960), 1292-97. 102. LVO, fol. 55a. Origin, 1st ed., p. 76.

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Studiesof AnimalPopulationsfrom Lamarckto Darwin usually do not flourish as well as native ones.103Some species, which in nature exist only in poor soil, grew more vigorously if planted in rich soil.104 Apparently, these species could not compete in the wild with species which were growing in rich soil.

Darwin warned against overemphasizing the role of competition in nature, giving instances in which the existence of numerous individuals of a species did not result in a greater struggle, but rather was necessary for the survival of the species. Some species of plants might be poorly pollinated, or have all their seeds eaten by animals, if they did not grow in dense clusters. Many kinds of animals exist in herds, their numbers affording protection against predation.105The necessary sociality of some species would explain why they were abundant up to the limits of their range, whereas most species gradually become less numerous toward the limits of their range.'06 Darwin began discussing "checks to increase in aninals" with an example of how parasites can sometimes be a limiting factor. The impressive increase of feral cattle and horses on the pampas of La Plata had not been duplicated in Paraguay because of a "fly there, which lays its eggs in the navel of the newly born young."107 Mosquitoes cause the death of reindeer, and maggots limit the numbers of toads.'08When Darwin was writing this draft plant pathology had not made much progress, and he thought that plant parasites were of less importance than animal parasites.'09 When other factors did not

liimit animal numbers, there often appeared "mysterious epidemics, which seem connected we know not how, with the closer aggregation of many individuals of the same kind."110 Predationwas one of the most obvious limiting factors for animals, and Lyell had explained that it does not operate in a simple way. The classic (though apparently inaccurate"') il103. LVO, fols. 42v, 42, 43. 104. LVO, fol. 47. Herbert, "Habitations," p. 46. 105. Darwin also discussed cooperation in The Descent of Man, and Selection in Relation to Sex, 2 vols. (London: John Murray, 1871; 2nd ed., 1 vol., 1875), chap. 4. Darwin's comments on cooperation in nature are discussed by Arthur Keith, Darwin Revalued (London: Watts, 1955), chap. 21; and by Ashley Montagu, Darwin: Competition and Cooperation (New York: Schuman, 1952). 106. LVO, fols. 59a-62. 107. LVO, fol. 19. 108. LVO, fol. 23. 109. LVO, fol. 41. 110. LVO, fol. 35. 111. Origin, 1st ed., p. 74. W. L. McAtee has questioned the validity of the report: "The Cats-to-Clover Chain," Sci. Monthly, 65 (1947), 241-242. Darwin got the account from H. W. Newman, "On the Habits of the Bombinatrices," Entomol. Soc. London, Trans., n.s., Proceedings Section, 1 (1850-51), 86-92, 109-112, 117-118; see p. 88.

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lustration of the repercussions from predation is the cats-toclover chain which Darwin cited: What animals can seem less concemed with each other than a cat & Humble-Bee; yet Mr. [H. W. Newman] shows that field mice are the most powerful enemies to the Bee, & the cats determine the number of mice, as everyone knows in his house, & hence he believes that Humble bees are apt to abound near villages, owing to the destruction of the mice.112 Darwin was somewhat overawed by the ramifications of predator-prey relationships and believed them too complicated to be completely unraveled. He did, however, attempt to understand how these relationships work. If a predator increased out of proportion, he reasoned, its prey would become scarce, and this would then reduce the predator's numbers. If a species maintained a fairly constant population within the limiting factors of its environment, then the addition of another check without a compensatory relief would eventually result in its extinction. "But the rate of decrease will be very slow: if we have 1000 individuals & we destroy on an average ten per cent more every year at the period when the number is least than were heretofore destroyed, it will take 298 years to reduce the number to fifty." 113 Animals hunted for their fur inevitably declined in numbers, as had whales with the development of the whaling industry. On the other hand, since their predators were also controlled, the game animals in England did not diminish with increased sport-hunting. The relationship between an herbivorous animal and its food plants is often similar to that between a predatory animal and its prey. Darwin treated this subject under the heading "Mutual checks of animals & plants." Linnaeus had observed that most herbivores are selective feeders, with cattle usually feeding on different herbs from those eaten by insects.'14 Lyell had implied and Darwin suggested that if both insects and cattle feed on the same species, it would probably be exterminated.115 The same relationship between the numbers of predatory animals and their prey existed between the numbers of herbivores and plants. The far-reaching effects of these relationships could best be observed where man has tampered with the natural community. Although not dwelling upon this to the extent that Lyell had, Darwin furnished some apt illustrations. The selective feeding of the cattle introduced into La Plata had radically altered the pattern of the vegetation."16 The goats and swine 112. LVO, fol. 24. 113. LVO, fol. 34. 114. Linnaeus, "Oeconomy," pp. 95-100. 115. LVO, fol. 38. 116. LVO, fol. 37.

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Studies of Animal Populations from Lamarck to Darwin brought to St. Helena Island had destroyed all the tree seedlings for two hundred years, after which there were no trees left, and eight species of snails which had lived in the trees had also become extinct.117 Conversely, the introduction of trees into the heath-land greatly increased the insect and bird life of the area.118Animals depending upon vegetation only for protection were also affected by these alterations: According to Nillsson wolves have of late increased in Halland & foxes decreased; & this it is believed is chiefly owing to the wolves running down & devouring the foxes, as has often been witnessed; but they can do this only on open plains, so that the proportional increase & decrease of wolves & foxes here depends indirectly on the presence of trees.119 This example also indicates the effects of community succession upon the populations of its species. Darwin thought that "all plants in a state of nature undergo a kind of rotation of crops, exhausting one spot & spring up in another, being supplanted & supplanting others." 120 But he did not realize, as Linnaeus had,121 that these successions are predictable and follow fairly definite sequences. Darwin detected one of the possible causes of "rotation:" Many curious accounts have been published of the change of vegetation when a N. American forest has been bumt or cut-down & then left to nature. This has been called rotation; & it seems pretty clear that in our meadows & woods, when not suddenly destroyed that there is a real rotation, like that followed by farmers & probably dependent on the same causes, viz chiefly exhaustion of the various chemical elements in the soil required in different proportions by the different families of plants.122 Another factor influencing succession which he mentioned was the availability of seeds. However, Darwin did not realize how 117. LVO, fol. 39. 118. LVO, fols. 49-50. 119. LVO, fols. 21-22. Llewellyn Lloyd, Field Sports of the North of Europe; Comprised in a Personal Narrative of a Residence in Sweden and Norway, in the Years 1827-8, 2 vols. (London: H. Colburn and R. Bentley; citation from 2nd ed., 1831), I, 395. 120. LVO, fol. 43. 121. Linnaeus, "Oeconomy," pp. 78-79, 44-45. 122. LVO, fols. 50-51. Darwin cited Alphonse Louis Pierre Pyramus de Candolle (1806-93), Geographie botanique raisonnde ou exposition des faits principaux et des lois concernant la disposition g6ographique des plantes de l'6qoque actuelle, 2 vols (Paris: Victor Masson; Geneva: J. Kessmann, 1855), I, 448, 472. Lyell had given references to studies of plant succession in bogs (PC, II, chap. 13), but Darwin apparently did not examine them.

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important for understandingsuccession was Forbes'sdiscovery that organisms tend to change their own environment because of their life processes. The importance of any one mortality factor in limiting a population,Darwin observed,often depended upon when it was operative.If during the winter a wolf killed a deer which would otherwise have starved, then the deer population had not been much affected. In fact, predation of this kind might even benefit the species by allowing those individuals which could survive the winter to have more food.123The greatest mortality in many species of animals is in the eggs or young,124and in plants, in the seed or seedling,'25 but other stages in life cycles are also vulnerable, such as the time of migration for many birds.128 The number of eggs or seeds an organism producesis an index, not of its abundanceas some had thought, but ratherof the chances which its offspringhave for survival.127 The effect of climate as a limiting factor can, like predation, be more complex than casual observation might indicate. For instance, the range of some species appeared to be limited only indirectly by it, in that they were less efficient in competing with other species in adverse climates.128The limitation might only occur every few years, as was true of the droughts of La Plata. The situation there was complicated by the increase of mice while the cattle, birds, and so on were decreasing.'29 The mortality of English songbirds increased during the occasionalcold winters.130 Before the third draft of the Origin, containing the above observations, was completed, Darwin received the famous letter from Wallace, which brieflyoutlined the principle of natural selection and resulted in their joint article being published by the Linnean Society.'13 Rather than delay further over the documentationof his evidence, Darwin published his work in an abridgedform which became the first edition of On the Origin of Species (1859). In some of his later books, he utilized parts of the long version which he had not put into the Origin. However, the chapter on the struggle for existence, containing most

of his observations on population dynamics, he never fully utilized in either the published version of the Origin or elsewhere.'32He had intended to do so, because he wrote in the 123. LVO, fols. 34-35. 124. LVO, fol. 29. 125. LVO, fol. 43. 126. Darwin cited Gilbert White (1720-93), The Natural History and Antiquities of Selborne (London: B. White and Son, 1789; many later eds.), letter to Damnes Barrington no. 16. 127. LVO, fols. 25, 29-30, 65-66. 128. LVO, fol. 47. 129. LVO, fols. 19-20. 130. LVO, fols. 26-27. 131. Cited above, note 90. 132. Stauffer, "'On the Origin of Species:' An Unpublished Version,"

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Studies of Animal Populations from Lamarck to Darwin Origin that "in my future work this subject shall be treated, as it well deserves, at much greater length." 133 But even without a later development of these ideas, they were published in enough detail in the Origin to furnish a stimulus to other biologists. Summary and Conclusions Darwin's theory of evolution brought to an end the static view of nature. It was no longer possible to think of species as immortal, with secure places in nature. Fluctuation of population could no longer be thought of as occurring within definite limits which had been set at the time of creation. Nor was it any longer possible to generalize from the differential reproductive potentials, or from a few cases of mutualism between species, that everything in nature was "fitted to produce general ends, and reciprocal uses." 134 The appeal to "design" could no longer be substituted for answers to questions concering animal demography. Instead, the dynamics of a population had to be viewed as the outcome of species' struggle against animate and inanimate factors in the environment. Both the members of a species and the environmental factors tend to vary randomly, and therefore neither evolution nor population dynamics could be fully understood alone. For this reason Darwin's linking of the two subjects was inevitable and not merely an historical accident. Since Darwin had shown that no automatic equilibrium existed, he demonstrated the importance of closer study of the causes of population dynamics and extinction. He also indicated that an understanding of population depends upon the development of a broad knowledge in ecology. Viewed from another direction, Darwin's work ended the early modern era of population studies by clarifying three interrelated problems which were important for understanding population: extinction, distribution, and the nature of species. The components of his answer had been discussed in the eighteenth century, but there had not existed enough evidence for the compp. 1149-52. Wallace had access, courtesy of Darwin's son Francis, to some of Darwin's unused notes in 1889, but there is no indication that he utilized the LVO chapter on "the struggle for existence." Wallace, Darwinism: An Exposition of the Theory of Natural Selection with Some of Its Applications (London and New York: Macmillan, 1889), p. viii and chap. 2. 133. Origin, 1st ed., p. 62. 134. Linnaeus, "Oeconomy," p. 39. Linnaeus' assumption is compatible with the idea of "guided" evolution. Darwin rejected this idea in a letter to Lyell, 21 August 1861. More Letters, I, 194, letter 132.

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pletion of the revolution in thought which had then begun. At the beginning of the nineteenth century, Playfair found the evidence for extinction conclusive, and, in spite of Lamarck, Cuvier convinced the scientific world that there could no longer be any doubt about it. This was a step the importance of which, with his limited knowledge of biogeography and population, Cuvier could not have fully realized. Lamarck attempted, with his evolutionary theory, to circumvent the necessity for admitting extinction, but he overestimated the adaptability of organisms and in doing so he underestimated the importance of competition and the whole field of ecology. On the other hand, he was not willing to let questions such as the origin of species remain taboo to science. The origin of species was a biogeographical as well as a paleontological question. Humboldt correlated environment with the distribution of species and conveyed the impression that plant communities are subject to change. De Candolle, following the lead of Linnaeus and Humboldt, emphasized the ecological aspects of biogeography, not only the importance of habitat and range, clearly showing the ecological effects of competition. The entomologists Kirby and Spence took a faltering step toward understanding the relationship between population and ecological role, but they fell short of any significant new conclusions. Neither they nor Swainson could fully comprehend the new perspective of De Candolle. Lyell was able to bring together the evidence from these three lines of investigation and weave them into an important synthesis that almost accomplished what Darwin later did. Although opposing Lamarck's theory of evolution, Lyell had a dynamic view of ecology. He realized that population dynamics offered an important key to the understanding of biogeography. Since he knew that species become extinct, he investigated closely the factors which could either preserve or extinguish species. While explaining these factors, he described the interrelationships of species in greater detail than had ever been done before. Forbes continued to develop Lyell's ecological concepts, and his first-hand field experience enabled him to describe biotic communities more concretely than Lyell had. Having the advantages of Lyell's understanding and his own experience from a global voyage, Darwin could take the final step from the static to the dynamic concept of life. He had seen populations fluctuating and also fossil species in South America, and on the Galapagos Islands he had encountered a biogeographical problem that could not be credibly solved without the idea of evolution. However, the bare idea of evolution

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Studies of Animal Populations from Lamarck to Darwin did not fully answer his questions. He sought physiological causes of extinction before he read Malthus and realized that De Candolle and Lyell had correctly emphasized the importance of competition. Darwin found that, in order to understand evolution, he needed to improve his understanding of ecology. He wanted to know when populations were most easily decimated, how extensive were competition and cooperation, what effects parasites have upon populations, and what changes occur in biotic communities when a species is either added or subtracted. He contributed to some extent to answering these questions. Though there remained much for others to do, there was now a new and more secure theoretical framework within which later studies could be interpreted. As Ernst Mayr has observed, Darwin's "consistent thinking in terms of population has had an impact on biological theory and practice which is second only to his sponsorship of natural selection as the mechanism of evolution." 135 135. Mayr, 'Foreword," in Gavin de Beer, Charles Darwin. A Scientific Biography (London, New York: Thomas Nelson and Sons, 1963; new ed., Garden City: Doubleday, 1965).

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Wallace,Darwin,and the Theoryof NaturalSelection A Studyin the Developmentof Ideas and Attitudes BARBARA G. BEDDALL 2502 Bronson Road, Fairfield, Connecticut

INTRODUCTION On 1 July 1908 the Linnean Society of London commemorated the reading before the Society fifty years earlier of the DarwinWallace joint papers, "On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection." 1 On the first occasion only some thirty Fellows and guests had been present at a quiet, unheralded meeting; the authors themselves were absent. Now there was a large and distinguished gathering celebrating the historic event. Two of the original cast were present, the naturalist Alfred Russel Wallace (1823-1913) and the botanist Sir Joseph Dalton Hooker (1817-1911). The other two, the biologist Charles Robert Darwin (1809-1882) and the geologist Sir Charles Lyell (1797-1875) had been dead for many years. Hooker, now a venerable nonagenarian, spoke of his "halfcentury-old real or fancied memories" of that June in 1858 when his old friend Darwin received Wallace's paper on natural selection. He based his account on Sir Francis Darwin's Life and Letters of Charles Darwin, remarking with some uneasiness that, beyond the letters from Darwin to himself and to Lyell, no other documentary evidence existed of the events of those turbulent weeks before the reading of the papers. Despite a search, the letters to Darwin from Hooker and Lyell could not be found, "and, most surprising of all, Mr. Wallace's letter and its enclosure have disappeared." 2 1. Linnean Society of London, The Darwin-Wallace Celebration held on 1st July, 1908, by the Linnean Society of London (London; The Society, 1908). 2. Francis Darwin, ed., The Life and Letters of Charles Darwin, including an Autobiographical Chapter (London: Murray, 1887; reprinted

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Hooker was troubled by the meagerness of the evidence, but Marchant, Wallace's first biographer, was unconcerned, and most people have concurred in his opinion that the eight extant letters received from Darwin while Wallace was in the Malay Archipelago "explain themselves and reveal the inner story of the independent discovery of the theory of Natural Selection." 3 But do they? A second question pertains to the relationship between Wallace and Darwin. Their recollections are often taken to be accurate reflections of their earlier thoughts and actions, but details may have been altered and the emphasis changed. Both men did come to play the roles assigned to them by history, but the making of the myth, in which they both participated, has obscured some of the facts. This study will emphasize Wallace and the influences on him. It will attempt to disentangle the various lines of evidence, to trace Wallace's progress toward the discovery of the theory of natural selection, to throw some light on what happened both before and after June 1858, and to suggest some alternatives to commonly accepted theories about these events. It is based on a re-evaluation and reinterpretation of contemporary sources, both published and unpublished. Because the aim has been to concentrate on primary source material, exhaustive reference to every author who has written since on these subjects has not been attempted. In particular, three of Wallace's published papers are considered in detail: "On the Law which has regulated the Introduction of New Species," "Note on the Theory of Permanent and Geographical Varieties," and "On the Tendency of Varieties to depart indefinitely from the Original Type." A number of previously published letters bear on questions raised here. For ease of reference, information about these letters has been arranged in tabular form in the Appendix and the letters numbered consecutively. They will be referred to by numbers in brackets in the text, with further discussion when required in appropriate footnotes. Use has also been made of a manuscript notebook kept by Wallace during his travels in the Malay Archipelago, and I am grateful to Mr. Thomas O'Grady and the Council of the Linnean Society of London for permission to quote from it. in 2 vols., New York, Basic Books, 1959); Linnean Society of London, The Darwin-Wallace Celebration, p. 16. See also notes 115 and 139. 3. James Marchant, Alfred Russel Wallace: Letters and Reminiscences (New York: Harper, 1916), p. 105.

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Wallace, Darwin and the Theory of Natural Selection I. AN INQUIRING MIND He who in place of reasoning, employs authority, assumes that those to whom he addresses himself are incapable of forming a judgment of their own. If they submit to this insult, may it not be presumed they acknowledge the justice of it? Wallace, "Notebook, Fallacies4

1855-1859,"

from Jeremy

Bentham's

Book of

Not until 1841, when he was eighteen years of age, did Alfred Russel Wallace, the eminent naturalist, begin his solitary study of the natural world around him. As a frequently unemployed and always impecunious surveyor, he turned to the study of plants to fill his leisure time: But what occupied me chiefly and became more and more the solace and delight of my lonely rambles among the moors and mountains, was my first introduction to the variety, the beauty, and the mystery of nature as manifested i the vegetable kingdom.5 Wallace's early years and education were quite undistinguished. The eighth child of an increasingly impoverished family, he was born on 8 January 1823 in the remote village of Usk in Monmouthshire, Wales. When he was five, the family moved to Hertford, near London, and it was at the Hertford Grammar School that he received his "very ordinary education." This ended when he was almost fourteen, and after that he was more or less on his own. Despite his commonplace upbringing, however, he had received a priceless gift from his father: a love of books and reading-a key to the world for anyone who wants to use it. After a few months spent with his brother John in London in the spring of 1837, Wallace joined his oldest brother, William, to learn land surveying. But these were lean years for William, just before the rush of activity brought on by the construction of railroads, and he often had difficulty in finding enough work for himself and his younger brother. During one lull in 1839, Wallace spent some months learning the watchmaking trade. Fortunately, business changes brought this to an end before Wallace was formally apprenticed, and he returned to surveying with William. 4. Alfred Russel Wallace, "Notebook, 1855-1859," MS, Linnean Society of London, p. 102. This and other quotations are reproduced with permission from the Wallace and other manuscript material in the Library of the Linnean Society of London. 5. Alfred Russel Wallace, My Life: A Record of Events and Opinions (New York; Dodd, Mead, 1905), I, 191.

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Two years later, in 1841, Wallace purchased his first book on natural history, a shilling pamphlet on botany published by the improbablynamed Society for Promoting the Diffusion of Useful Knowledge. This quickly became his constant companion on his rambles through the countryside. Eager now to learn more, he was attractedby an advertisementfor a textbook by one of England's experts, The Elements of Botany by John Lindley. But this expensive purchase, which arrived in July 1842, was a disappointmentbecause it described all the orders of plants without indicating the British species. Not deterred, Wallace, with the aid of Loudon'sEncyclopaediaof Plants, set about annotating his copy of Lindley, thereby giving himself the rudimentsof a botanicaleducation.6 How Wallace first happened upon Darwin's Voyage of the Beagle is not known, but he tipped quotations from the first edition into his copy of Lindley. He was apparentlystruck by Darwin's comment that to receive the fullest enjoyment from the passing scene, "a traveller should be a botanist, for in all views plants form the chief embellishment."7 Still another purchase made about the same time was Swainson's Treatise on the Geography and Classification of Animals, a remarkable

assembly indeed for someone with no biological background whatever.8

William's business did not improve, and Wallace again left to look for something else. Early in 1844 he settled upon teaching at the Collegiate School in Leicester. Teaching proved enjoyableenough, but this periodis importantfor other reasons. The town of Leicesterboasted a good library, and Wallace was soon spending his free time there reading, among other things, Humboldt's Personal Narrative of Travels and Malthus' Essay on the Principle of Population.9 6. John Lindley, The Elements of Botany, Structural, Physiological, Systematical, and Medical: Being a Fourth Edition of The Outline of the First Principles of Botany (London: Taylor and Walton, 1841); Wallace's copy is in the library of the Linnean Society of London. John Claudius Loudon, Encyclopaedia of Plants (London: Longman, 1829-1840). 7. Charles Darwin, Journal and Remarks, 1832-1836 (vol. 3 of Robert Fitzroy's Narrative of the Surveying Voyages of His Majesty's Ships 'Adventure' and 'Beagle,' . . . London: H. Colburn, 1839), p. 604. Because the titles of the first and second editions differ, the short title used here for both will be Voyage of the Beagle. See also notes 39-41, 43 and Appendix, 69. 8. William Swainson, Treatise on the Geography and Classification of Animals (London: Longman, 1835). Wallace's copy is in the Library of the Linnean Society of London. 9. Alexander von Humboldt and Aim6 Bonpland, Personal Narrative of Travels to the Equinoctial Regions of the New Continent, tr. H. M. Wilwhich edition Wallace read is liams (London: Longman, 1814-1829);

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Wallace, Darwin and the Theory of Natural Selection Most important of all was the friendship of another young amateur naturalist, the entomologist Henry Walter Bates (18251892). Bates, two years younger than Wallace, had similarly finished his formal education at the usual early age. But, though apprenticed to a hosiery manufacturer in Leicester, he had enrolled in the local Mechanics' Institute, one of many such schools set up for the further education of workingmen. Here he made the acquaintance of several naturalists and soon plunged enthusiastically into the study of entomology. By the time he met Wallace he had already published his first short paper.'0 For the first time Wallace had someone with whom to talk over his discoveries. And Bates soon introduced him to the wholly new world of insects. Wallace was overjoyed. In short order he equipped himself with collecting bottles and pins and a copy of Stephens' Manual of British Coleoptera and embarked on this fascinating new study.'1 This happy period ended abruptly when Wallace's brother William died unexpectedly in February 1846.12 Wallace left the school to help settle his affairs, and in January 1847 his second brother, John, joined him in carrying on the business. Wallace was irked by the details of management, formerly handled by his oldest brother. And he was also cut off from his new-found friends in Leicester, as he wrote plaintively to Bates [1].13 The time was not wasted, however. Wallace's letters to Bates show the extraordinary progress in his reading [1-4I14: Darnot known. Thomas Robert Malthus, An Essay on the Principle of Population, 6th ed. (London: Murray, 1826). Which edition Wallace read is not known; in 1908 he took his references from the 6th. According to De Beer ("Darwin's Notebook," part 4, 30n), this is the edition that Darwin read. 10. Henry Walter Bates, "Note on Coleopterous Insects Frequenting Damp Places," Zoologist, 1 (1843), 114-115. 11. James Francis Stephens, Manual of British Coleoptera (London: Longman, 1839). 12. There is some question about the date of William's death. In Wallace's autobiography (My Life, I, 239), he gives it as 1846, but he also said he spent only one year at Leicester and correspondingly longer at Neath. In an attempt to straighten out this discrepancy, Poulton persuaded Wallace's son that William must have died in 1845; see E. B. P[oulton], "Alfred Russel Wallace, 1823-1913," Proc. Roy. Soc. London, [95B] (1923-1924), viiin. 13. Numbers in brackets refer to the letters listed in the Appendix. Where additional discussion of the letters is required, it will be found in appropriate footnotes. 14. The dates of letters nos. 2 and 3 are uncertain, and there is no compelling evidence to settle the matter. McKinney, following Clodd, has placed them in 1845; see H. Lewis McKinney, "Alfred Russel Wallace and the Discovery of Natural Selection," J. Hist. Med. Allied Sci., 21 (1966),

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win again, Lyell's Principles of Geology, Vestiges of the Natural History of Creation by the then anonymous author, Robert Chambers, Lawrence's Lectures on Man, and Prichard's Physical History of Man.15 Wallace was already caught up in the more philosophical questions of evolution, the origin and distribution of species, and the differences between species and varieties. What a giant step forward from the shilling pamphlet on botany purchased only six years beforel But an even greater step was in store. Late in 1847, Wallace and Bates read an "unpretending volume," A Voyage up the River Amazon, by a young American amateur naturalist, W. H. Edwards.'6 Already dissatisfied with their prospects at home, they wondered if they could make such a trip. Inquiries at the British Museum about the feasibility of the scheme brought assurances that there was a ready market for anything they might collect in this little-known region. At once they determined to go. But even as early as this their interests were not limited to collecting. Wallace was already interested not only in the differences between species and varieties, but also in the origin of species, and just before they left he wrote to Bates that he had begun to "feel rather dissatisfied with a mere local collection; little is to be learnt by it. I should like to take some one family to study thoroughly, principally with a view to the theory of the origin of species. By that means I am strongly of opinion that some definite results might be arrived at [3, 4]." 17 The two young adventurers left England in April 1848, arriving a month later at Pari (now Belem) at the mouth of the 337 n25. See also note 12. Marchant, in his Wallace, pp. 73-74, puts them in 1847, and that date is used here. 15. Charles Lyell, Principles of Geology: or the Modern Changes of the Earth and Its Inhabitants (London: Murray, 1830-1833, and later editions). Robert Chambers, Vestiges of the Natural History of Creation (New York: Wiley and Putnam, 1845, from the 1st English ed., 1844). Darwin, among others, held a low opinion of the Vestiges; see Appendix, 14 and note 92. William Lawrence, Lectures on Physiology, Zoology, and the Natural History of Man (London: Printed for J. Callow, 1819, and later editions). James Cowles Prichard, Researches into the Physical History of Man (London: J. & A. Arch, 1813, and later editions). Darwin also read both Lawrence and Prichard (De Beer, "Darwin's Notebook," part 2, 107n). 16. William Henry Edwards, A Voyage up the River Amazon (London: Murray, 1847). 17. See Appendix; also note 97. McKinney ("Wallace and Natural Selection," p. 337) has also pointed out Wallace's early interest in species, but he overlooked the significance of the related question of species and varieties; see Sec. III and note 105.

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Wallace, Darwin and the Theory of Natural Selection Amazon River. (It is worth noting that they had no benefactors, financial or otherwise, and that they had no resource but themselves. Darwin, on the other hand, was attached to an official government mission and was able to pay his personal expenses himself.) Wallace remained for four years, returning to England in October 1852; Bates stayed eleven, not arriving home until July 1859. For the first few months, while they were becoming familiar with their new surroundings, they traveled together. Then they parted company, each traveling independently from then on. Wallace journeyed up the Amazon and the Rio Negro to the place where the latter joins the Orinoco, a spot already made famous as the farthest point reached by Humboldt coming from the other direction. Bates chose to go to the Upper Amazon, spending considerable time at Ega, 1400 miles upstream from the Atlantic Ocean. These intrepid explorers were entirely on their own in the strange and oftentimes forbidding tropics of Brazil, contending with an uncertain supply of food, hazardous travel, indolent or dishonest natives (spoiled, they thought, by being half-civilized), illness, and isolation. They financed their exploits by the sale in Europe of duplicate collections, mainly of insects. Unfortunately, the scientific and financial results of Wallace's travels were disappointingly meager, but with reason. Owing to a misunderstanding, the specimens collected during the last two years were still waiting unshipped when he returned to Barra (now Manaus) on his way back to England. And so, unhappily, these as well as the richest part of his private collections were on board with him when the ship caught fire at sea. Nearly everything was lost as passengers and crew rushed to leave the burning vessel, some 700 miles off Bermuda. Wallace and his companions were forced to spend ten days in open boats before they were finally rescued by a passing freighter. As a consequence of this disaster, Wallace had to piece together the few papers and two books that he wrote on his return home from letters, a few rescued notes, and his memory. He pursued his growing interest in the geographical distribution of animals in papers on the monkeys and the butterflies of the Amazon Valley, remarking on limits and barriers to their distribution and on the importance of labelling specimens with the exact locality where they were found for the proper study of this distribution.18 Besides a small book on the palm 18. Alfred Russel Wallace, "On the Monkeys of the Amazon," Proc. Zool. Soc. London, 20 (1852), 107-110; and "On the Habits of the Butter-

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trees of the region, he also wrote the story of his expedition, A Narrative of Travels on the Amazon and Rio Negro.19 It is a tale of high adventure but, due to the loss of so much of his material, it is less rewarding from a scientific point of view. Bates was more fortunate, although he took good care to send his last collections home on three ships instead of one. On his return, he wrote a series of papers on the insect fauna of the Amazon Valley, in one of which he developed his famous theory of protective coloration, still known as Batesian mimicry.20 His account of his travels, The Naturalist on the River Amazons, was more scientific than Wallace's and also, to Wallace's chagrin, more successfUl.21 But Wallace's misfortune proved a boon after all. He had counted on the money from the sale of the lost collections; without it he faced a return to surveying or another trip. Fortunately for both himself and the world, he chose the latter course, deciding after much study that the Malayan region offered the opportunities he sought. And so, in the spring of 1854, he set off again, on the eight-year exploration of the tropics on the other side of the world "which constituted the central and controlling incident of my life." 22 Once again Wallace had to make do with things as he found them, accommodate himself to local customs, learn native languages, find food and shelter where he could, and use any available means of travel. As a practical matter, the weather and traveling arrangements largely determined his itinerary. The first two years were spent around Singapore and in Borneo, the next five in the area from Celebes to northern New Guinea, and the last year in Timor, Java, and Sumatra. A particular aim this time was a more thorough investigation of the problems of the geographical distribution of animals. Wallace had chosen well, for the lessons of an island world flies of the Amazon Valley," Trans. Entomol. Soc. London, N.S. 2 (18521853), 253-264. 19. Alfred Russel Wallace, Palm Trees of the Amazon and Their Uses (London: J. Van Voorst, 1853); and A Narrative of Travels on the Amazon and Rio Negro (London: Reeve, 1853). 20. Henry Walter Bates, "Contributions to an Insect Fauna of the Amazon Valley. Lepidoptera: Heliconidae," Trans. Linn. Soc. London, 23 (1862), 495-515. 21. Henry Walter Bates, The Naturalist on the River Amazons (London: Murray, 1863). Many of Bates' more interesting comments on the origin of species and on geographical distribution were omitted from the 2nd abridged edition (1864). 22. Wallace, My Life, I, 336.

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Wallace, Darwin and the Theory of Natural Selection are even more vivid than those of a continental region; Darwin had also discovered this when he visited the islands of the Galapagos Archipelago. Although Wallace was again supporting himself by the sale of duplicate collections, his theoretical interests were never far from his mind. The most spectacular result of this second trip was the independent discovery of the theory of natural selection, but this was only one of many important contributions to evolutionary theory. And happily enough, his discerning and wellwritten account of the region, The Malay Archipelago, became a worthy rival to Darwin's Voyage of the Beagle and Bates's Naturalist on the River Amazons.23 The three papers of special importance in tracing the development of Wallace's ideas on natural selection will now be considered in detail. II. THE "LAW" To discover how the extinct species have from time to time been replaced by new ones down to the very latest geological period, is the most difficult, and at the same time the most interesting problem in the natural history of the earth. The present inquiry, which seeks to eliminate from known facts a law which has determined, to a certain degree, what species could and did appear at a given epoch, may, it is hoped, be considered as one step in the right direction towards a complete solution of it. Wallace, "On the Law which has regulated the Introduction Species"

of New

Wallace's "powerful essay," 24 "On the Law which has regulated the Introduction of New Species," was published in September 1855, but to his disappointment it attracted little notice at the time.25 He had written it in the preceding February during a lull in his collecting activities, induced by the publication of Edward Forbes's theory of polarity, and he had hoped at the least for some comment from this brilliant young naturalist; unknown to Wallace, however, Forbes had died in November 1854. Except for Bates's, other response was minimal, if not disparaging. Wallace phrased his 'law" as follows: Every species has come into existence coincident both in space and time with a pre-existing closely allied species.26 Although the evolutionary 23. Alfred Russel Wallace, The Malay Archipelago: The Land of the Orang-utan, and the Bird of Paradise: a Narrative of Travel, with Studies of Man and Nature (London: Macmillan, 1869). 24. Thomas Henry Huxley, in Darwin, Life and Letters, 1, 539. 25. Alfred Russel Wallace, "On the Law which has regulated the Introduction of New Species," Ann. Mag. Nat. Hist. [2], 16 (1855), 184-196.

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implications of this statement are obvious, Wallace at this time had no suggestions on a mechanism of change. His speculations were rooted in his long-standing interest in the geographical distribution of animals and colored by his extensive practical experience in the tropics of two hemispheres. The study of zoogeography, in which Wallace was to become an acknowledged master, was still clouded in mystery when he first came upon it in Swainson's Treatise on the subject: We may, indeed, build a theory upon every thing in nature: but the more we investigate, the stronger will be our conviction in the following deduction: -That the primary causes which have led to different regions of the earth being peopled by different races of animals, and the laws by which their dispersion is regulated, must be for ever hid from human research [to which Wallace wrote "no" in the margin]. This conclusion is strengthened by the inference which will be drawn from the facts we shall subsequently state; an inference so well expressed by a very intelligent writer, that we shall give it nearly in his own words. "It appears that various tribes of organised beings were originally placed by the Creator in certain regions, for which they are by their nature peculiarly adapted [Wallace's underlining]." 27 In a modification of the quinarian system of William Sharpe Macleay, Swainson divided the earth into five regions according to what he believed to be the five major races of mankind; animal groups were likewise divided into fives. The divisions were mathematical, the reasons not only unknown but unknowable. But Wallace questioned Swainson from the first, noting that "there appears not to be the slightest reason for believing a priori that all groups of animals are divided into 28 the same number of types of forms or divisions .. Over the years Wallace's ideas matured. Traces of this can be found, as mentioned earlier, in his papers on the monkeys and the butterflies of the Amazon Valley, as well as in his Narrative, but he was undoubtedly handicapped by the loss of so much of his South American material. The appearance of Forbes's paper spurred Wallace to collect and organize his thoughts, for Forbes's theory of polarity as an explanation of organic changes through geologic time seemed as untenable 26. Ibid., p. 186. 27. Swainson, Treatise on Geography, p. 9. 28. Note written by Wallace in his copy of Swainson's Geography, p. 223.

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Treatise

on

Wallace, Darwin and the Theory of Natural Selection to him as had Swainson's theories about the present geographical distribution of animals. A pervading influence on Wallace, one might almost say the pervading influence, was Charles Lyell's Principles of Geology. Wallace had read Lyell at least as early as 1846, and he had accepted wholeheartedly Lyell's application of the principle of uniformitarianism to geology. But Lyell's influence was more profound than that. From the notebook kept by Wallace during his Malayan travels, it seems that he had with him a copy of the fourth edition of Lyell's Principles, and the discussion here refers to this edition.29 In a large measure, Wallace's "Notebook" is a long, private argument with Lyell, refuting many of the latter's biological theories. Wallace was thus stimulated to broaden and deepen his own thinking. It should be noted in Lyell's defense, however, that he was neither a trained biologist nor a collector of living specimens (although he had collected insects as a youth), and that he lacked the extensive first-hand experience with living things acquired through long years by a Lamarck, a Darwin, or a Wallace. It has often been said that Lyell nearly stumbled onto evolutionary theory himself; it has even been suggested that he was an evolutionist in secret, at least at first.30 But in fact he was far removed at many critical points. He had missed altogether the crux of Wallace's paper-the relationship of species in both time and space-and so a theory of descent was not only not a logical deduction, it was irrelevant. On his own terms he believed he had applied the principle of uniformitarianism to organic changes by showing the gradual extinction and creation of species. But he believed firmly in the stability of species, scarcely a good foundation for a theory of evolution. Lyell was well acquainted, however, with Lamarck's theory of the transmutation of species, having first read it in 1827. Although he found the ideas provocative, he confessed in a letter to Mantell that "I read him rather as I hear an advocate on the wrong side, to know what can be made of the case in good hands."31 He included a lengthy summary in his Prin29. Lyell, Principles of Geology, 4th ed. (London: Murray, 1835). See also note 4. 30. Gertrude Himmelfarb, Darwin and the Darwinian Revolution (Garden City, N.Y.: Doubleday, 1959), pp. 180-189. An early proponent of this point of view was Thomas Huxley, in Darwin, Life and Letters, I, 543-548. 31. Katherine Lyell, ed., Life, Letters and Journals of Sir Charles Lyell (London: Murray, 1881), I, 168.

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ciples, at first in protest against the pretension that species were "capable . . . of being indefinitely modified in the course of a long series of generations," but later to give due honor to Lamarck and his evolutionary theories.32 Wallace and Darwin both read Lyell's summary. Parenthetically, it might be observed that Lyell accepted to a limited degree what later generations have considered the hallmark of Lamarckism, the inheritance of acquired characteristics. In Lyell's case, this meant the possible inheritance of acquired habits that remained within the strict limits of predetermined variation. To a limited extent, Darwin was also to accept this Lamarckian tenet, but Wallace never did. Lyell's view of geographical distribution was more comprehensive than Swainson's. He had broadened the scope to include time and change, although there was no hint of evoludon: If the views which I have taken are just, there will be no difficulty in explaining why the habitations of so many species are now restrained within exceedingly narrow limits. Every local revolution, such as those contemplated in the preceding chapter, tends to circumscribe the range of some species, while it enlarges that of others; and if we axe led to infer that new species originate in one spot only, each must require time to diffuse itself over a wide area. It will follow, therefore, from the adoption of this hypothesis, that the recent origin of some species, and the high antiquity of others, are equally consistent with the general fact of their limited distribution, some being local, because they have not existed long enough to admit of their wide dissemination; others, because circumstances in the animate or inanimate world have occurred to restrict the range which they may once have obtained. As considerable modification in the relative levels of land and sea have taken place in certain regions since the existing species were in being, we can feel no surprise that the zoologist and botanist have hitherto found it difficult to refer the geographical distribution of species to any clear and determinate principles, since they have usually speculated on the phenomena, upon the assumption that the physical geography of the globe had undergone no material alteration since the introduction of the species now living. So long as this assumption was made, the facts relating to the 32. Lyell, Principles of Geology, lst ed. (1832), II, 246.

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Wallace, Darwin and the Theory of Natural Selection geography of plants and animals appeared capricious in the extreme, and by many the subject was pronounced to be so full of mystery and anomalies, that the establishment of a satisfactory theory was hopeless.33 Although Lyell's biological theories were ambiguous and illdefined, his contributions to geology had added new dimensions to the history of the earth. In particular, he had expanded on the uniformitarian theory of the Scottish geologist James Hutton (1726-1797) that attempted "to explain the former changes of the earth's crust by reference exclusively to natural agents," 34 and he had vigorously attacked the commonly accepted belief that life on the earth had begun in the year 4004 B.C., as calculated by James Usher, Archbishop of Armagh. Wallace's efforts (and Darwin's too) would have been crippled without Lyell. Evolution was advocated, however, in a book published not long afterward, Vestiges of the Natural History of Creation. But its anonymous author, Robert Chambers, "a private person with limited opportunities for study," was no biologist either, and his popular work was ridiculed by scientists. Nevertheless, Wallace thought his hypothesis ingenious, as he wrote to Bates [2, 3]. For somewhat different reasons, two editions of Darwin's Voyage of the Beagle should also be included here. Wallace read the first edition (1839) quite early, perhaps as early as 1842 according to his first letter to Bates and the note in his copy of Lindley; and from evidence in the "Notebook," he took a copy of the second (1845) along with him to the Malay Archipelago. Wallace began his paper "On the Law" by noting the longcontinued series of geologic changes. Then, applying the uniformitarian principle to organic changes, he proposed "a like gradation and natural sequence from one geological epoch to another." 35 (Lyell had suggested the slow and gradual extinction and creation of species, but with no hint of descent.) From a series of propositions relating to "organic geography and geology," Wallace then deduced his 'law," which supported a hypothesis that might explain the past and present distribution of life upon the earth that had occurred to him, he said, about ten years earlier. First of the four main questions illuminated by Wallace's 33. Ibid., 4th ed., III, 165-166. 34. Ibid., 12th ed. (1875), 1, 73. 35. Wallace, "On the Law," p. 184.

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'law" was that perennial problem, "the system of natural affinities." 36 If the 'law" were true, species would be related to closely allied species which had preceded them. This relationship could rarely be expressed for long by a straight line. The divergence, uneven rates of change, and extinction of species, complicated by the fragmentary fossil record, could be better represented by a branching "as intricate as the twigs of a gnarled oak." 37 Artificial systems of classification based on circles or a fixed number of divisions were unnecessary contrivances. Lamarck would have agreed. He believed that species were defined by the gaps between them that were produced by extinction and by the fragmentary record, and that two or more diverging species would merge going backward in time. To Lyell this would have been unthinkable, convinced as he was of the real and permanent existence of species in nature. Next, in answer to the "singular phenomena" of the distribution of animals and plants in space, Wallace offered some original suggestions.38 He clearly recognized the part played by geographical isolation in the origin of peculiar forms of life in long-isolated places, and also the divergence from a widespread "antitype" that results in two or more representative forms in different regions of the world. He brought forward as examples the problems posed by the inhabitants of both ancient and recent island groups and mountain ranges. Of particular interest are Wallace's suggestions regarding the Galapagos Islands, where the "phenomena . . . have not hitherto received any, even a conjectural explanation." 39 Darwin had mentioned in the first edition of his Voyage of the Beagle the many peculiarities of distribution that he had found in this small archipelago, six hundred miles off the coast of Ecuador, concluding only: "But there is not space in this work, to enter on this curious subject." 40 Although Darwin expanded on this in the second edition of the Voyage, his remarks were again inconclusive: The only light which I can throw on this remarkable difference in the inhabitants of the different islands, is, that very strong currents of the sea running in a westerly and W.N.W. direction must separate, as far as transportal by 36. 37. notes 38. 39. 40.

Ibid., pp. 186-188. "Divergence" was an important part of Darwin's theory. See also 105, 111-113, 125-127, and Wallace, "On the Law," p. 187. Ibid., pp. 188-190. Ibid., p. 188. Darwin, Voyage of the Beagle (1839), p. 475.

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Wallace, Darwin and the Theory of Natural Selection sea is concemed, the southern islands from the northern ones; and between these northern islands a strong N.W. current was observed, which must effectually separate James and Albemarle Islands. As the archipelago is free to a most remarkable degree from gales of wind, neither the birds, insects, nor lighter seeds, would be blown from island to island. And lastly, the profound depth of the ocean between the islands, and their apparently recent (in a geological sense) volcanic origin, render it highly unlikely that they were ever united; and this, probably, is a far more important consideration than any other, with respect to the geographical distribution of their inhabitants. Reviewing the facts here given, one is astonished at the amount of creative force, if such an expression may be used, displayed on these small, barren, and rocky islands; and still more so, at its diverse and yet analogous action on points so near each other. I have said that the Galapagos Archipelago might be called a satellite attached to America, but it should rather be called a group of satellites, physically similar, organically distinct, yet intimately related to each other, and all related in a marked, though much lesser degree, to the great American continent.41 In other words, these islands were geologically recent, separated not only by deep ocean but also by currents, and without winds strong enough to have blown birds, insects, or seeds from one island to another. With no means of dispersal and a limited amount of time, it is no wonder that Darwin seemed puzzled. Actually, his private thinking was much in advance of this public statement, for he had already worked out his theory of natural selection as an explanation of the "creative force" at work in the islands, but Wallace had no way of knowing this.42 Wallace suggested, on the contrary, that these were islands of high antiquity that had been peopled by the agency of wind and water, as other islands were peopled, and that, the preexisting species having died out, only variously modified prototypes now remained. The islands of the Malay Archipelago differed in being separated by shallow seas (this was written shortly before Wallace discovered in the summer of 1856 the division between the Australian and Oriental Regions since 41. Charles Darwin, Journal of Researches into the Natural History and Geology of the Countries visited during the Voyage of H.M.S. Beagle round the World, 2nd ed. (London: Murray, 1845), p. 398. 42. Charles Darwin and Alfred R. Wallace, Evolution by Natural Selection (Cambridge: Cambridge University Press, 1958), pp. 116-121.

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immortalized as "Wallace's Line"), probably indicating an earlier land connection that could account for the basic similarities in their faunas. Islands like Great Britain, which had only recently (geologically speaking) been separated from continents, would have few groups peculiar to themselves. Wallace's reason for first writing Darwin in October 1856 can only be guessed at. Perhaps he hoped for some comment from Darwin on these suggestions. (An entry in his "Notebook" shows that he was rereading Darwin about this time. )43 Approaching the problem from another point of view, Wallace next considered the close geographical proximity of closely allied species in rich groups-such as the hummingbirds, toucans, palms, orchids, and various families of butterfliesand asked, "why are these things so?" These facts of distribution would not only be explained by his 'law," they would also be its necessary results. A corollary was that species have not arisen more than once, in two widely separated places. Lyell, for all his shortcomings in biology, had believed that species were "created" in one place only, although he recognized that this might give a false impression of centers of creation. Thirdly, Wallace inquired into the phenomena of geological distribution, the distribution of species in time rather than in space.44 Again he pointed out that proximity and gradual change were the rule and that species had been "created" only once. It is in connection with geological distribution, however, that reasons for Lyell's failure to hit upon evolutionary theory become clear. Especially important is the matter of the extinction of species. On this point Lyell and Lamarck represented two opposite points of view. Lyell, convinced of the immutability of species, could hardly believe otherwise than in their absolute extinction. He was applying the uniformitarian principle in extending backward in time the acknowledged present-day and probable future extinction of species: Although we have as yet considered one class only of the causes (the organic) by which species may become exterminated, yet it cannot but appear evident that the continued action of these alone, throughout myriads of future ages, must work an entire change in the state of the organic creation, not merely on the continents and islands, where the power of man is chiefly exerted, but in the great oceans, where his controul [sic] is almost unknown. The mind is pre43. Wallace, "Notebook," p. 60. See also notes 81, 103, and 162, and Appendix, 69. 44. Wallace, "On the Law," pp. 190-195.

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Wallace, Darwin and the Theory of Natural Selection pared by the contemplation of such future revolutions to look for the signs of others, of an analogous nature, in the monuments of the past. Instead of being astonished at the proofs there manifested of endless mutations in the animate world, they will appear to one who has thought profoundly on the fluctuations now in progress, to afford evidence in favour of the uniformity of the system, unless, indeed, we are precluded from speaking of uniformity when we characterize a principle of endless variation.45 Lamarck, on the other hand, considered that only a few large land animals at most had become extinct, and then through the agency of man. Even earlier than Lyell he had disagreed with the catastrophists, who thought that life had been wiped out at various times by universal cataclysms. Lyell suggested a course of gradual extinction and creation of species. But Lamarck had proposed that earlier species had gradually been changed into present-day species through transmutation; extinction thus played no important part in his system. Lyell, however, disagreed completely with Lamarck: To pursue this train of reasoning farther is unnecessary; the geologist has only to reflect on what has been said of the habitations and stations of organic beings in general, and to consider them in relation to those effects which were contemplated in the second book, as resulting from the igneous and aqueous causes now in action, and he will immediately perceive that, amidst the vicissitudes of the earth's surface, species cannot be immortal, but must perish, one after the other, like the individuals which compose them. There is no possibility of escaping from this conclusion, without resorting to some hypothesis as violent as that of Lamarck, who imagined, as we have before seen, that species are each of them endowed with indefinite powers of modifying their organization, in conformity to the endless changes of circumstances to which they are exposed.46 Wallace steered a middle course. He agreed with Lyell that some species might become extinct, but he also agreed with Lamarck that modified prototypes might remain. If extinction were the rule, as Lyell suggested, then some sort of "creation" was necessary to fill the gaps. Here Lyell was quite vague, his hypothesis on the original introduction of species reading as follows: Each species may have had its origin in a single pair, or 45. Lyell, Principles of Geology, 4th ed., III, 140-141. 46. Ibid., 155-156.

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individual, where an individual was sufficient, and species may have been created in succession at such times and in such places as to enable them to multiply and endure for an appointed period, and occupy an appointed space on the globe.47 This creation of new species was not readily seen because it was an infrequent occurrence taking place over a long period of time at differentplaces on the earth. Lamarck's solution to this problem was the mutability of species, though the agency he suggested-inheritance of characteristics acquiredthrough the will of the animal-was scoffed at even in his own day. The author of the Vestiges had still another suggestion: The idea, then, which I form of the progress of organic life upon the globe- and the hypothesis is applicable to all similar theatres of vital being-is, that the simplest and most primitive type, under a law to which that of like-production is subordinate, gave birth to the type next above it, that this again produced the next higher, and so on to the

very highest, the stages of advance being in all cases very small-namely, from one species only to another; so that the phenomenon has always been of a simple and modest character.48

Chambers'proposal that one species gave birth directly to the next higher brought derision upon his book. Nevertheless, he should at least be credited with having emphasized a natural method. Wallace, however, had no theory on how extinct species were replaced. For the present, he confined himself to "what species could and did appear."He saw that this was neither a random process nor a straight line from simple to complex, as proposed by the proponents of the theory of progressive development. A theory of gradual change combined with his 'law" would, he thought, account for the observed facts and even for apparentretrogressions. Lyell, as a geologist familar with the anomalies of the fossil record, had protested against the theory of progressive developmentbecause he disputedthe accuracyof the facts: It was before remarked, that the theory of progressive development arose from an attempt to ingraft the doctrine of the transmutationistsupon one of the most popular generalizations in geologv. But modem geological researches 47. Ibid., 99-100.

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48. Chambers, Vestiges, 1st ed., p. 167.

Wallace, Darwin and the Theory of Natural Selection have almost destroyed every appearance of that gradation in the successive groups of animate beings, which was supposed to indicate the slow progress of the organic world from the more simple to the more compound structure.49 Although evolutionary trends do exist (and Lyell later accepted a general progression), the record is far from straightforward, and its message is not easily read. The theory of evolution, with natural selection as an agent of change, was to make this record more comprehensible, for it postulates successful adaptation rather than any necessary progression. Wallace was still several years away from this answer, but he was heading in the right direction. It was Forbes's metaphysical theory of polarity that had prompted Wallace to set out his own thoughts.50 According to this theory, the distribution of organized beings (genera rather than species) in time manifested a quality known as polarity: an "arrangement in opposite directions with a development of intensity towards the extremes of each." 51 This relation was used to explain the larger number of generic forms in the earlier epochs of the Palaeozoic (Silurian and Devonian) and in the later epochs of the Neozoic (Cretaceous, Tertiary, and present), compared with the smaller number to be found in the intervening time. Wallace objected to this theory on several grounds. First of all, it invoked an obscure and hypothetical cause when "the facts may be readily accounted for on the principles already laid down." 52 In typical Lyellian style, he stressed the vast amounts of time involved and the action of natural causes, and he went on to propose that the rates of creation and extinction of species were related to unequal rates of geologic change, more species being created during quiet periods of the earth's long history and more becoming extinct during violent periods. Even more to the point was Wallace's criticism that Forbes's theory presupposed the completeness of the geological record (an error also made by those who believed in the theory of progressive development). Wallace knew it was fragmentary, but he would have been surprised to know that a century later fossils are still thought to represent less than one per cent of the species that have existed. Polarity's foundation was fragieleat best. 49. Lyell, Principles of Geology, 4th ed., III, 14-15. 50. Edward Forbes, "On the Manifestation of Polarity in the Distribution of Organized Beings in Time," Proc. Roy. Inst. London, 57 (October 1854), 332-337. 51. Ibid., p. 336. 52. Wallace, "On the Law," p. 192.

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The fourth and final point of Wallace's paper was another subject that had attracted much attention, the puzzling problem of rudimentaryorgans.53Lyell later admitted that he had missed their significance and as a result had omitted from his summary most of the examples given by Lamarck.54This is not surprising, however, because Lamarck had interpreted them in his own light, believing them to be the result of "the permanentdisuse of an organ, arising from a change of habits, [which caused] a gradual shrinkage and ultimately the disappearance and even extinction of that organ."56 Wallace, like Chambers, thought that rudimentary organs showed relationships, but he misinterpreted them, confusing vestigial with nascent organs. He did, however,ask the right question: "Ifeach species has been created independently, and without any necessary relations with pre-existing species, what do these rudiments,

these apparentimperfectionsmean?"se Wallace ended his paper grandly: "Granted the law, and many of the most important facts in Nature could not have been otherwise, but are almost as necessary deductions from it, as are the elliptic orbits of the planets from the law of gravitation."67 The response to it was hardly encouraging. More than two years passed before Bates's letter congratulating him arrivedfrom the Upper Amazon [9]. In the meantime, his agent, Samuel Stevens, wrote that he had heard several naturalists object to Wallace's "theorizing"when what was needed was more facts. III. THE'NOTE" . . . why should a special act of creation be required to call into existence an organism differing only in degree from another which has been produced by existing laws? Wallace, "Note on the Theory of Permanent and Geographical Varieties"

In the fall of 1857 Wallace sent off to the Zoologist a short paper entitled "Note on the Theory of Permanent and Geographical Varieties."58 The first part of his hypothesis had been his 'law" on "what species could and did appear";the 53. Ibid., pp. 195-196. 54. Lyell, Principles of Geology, 12th ed., II, 274. 55. Jean Baptiste Lamarck, Zoological Philosophy: an Exposition with Regard to the Natural History of Animals, tr. Hugh Elliot (London: Macmilan, 1914; reprinted, New York: Hafner, 1963), p. 115. 56. Wallace, "On the Law," p. 195. 57. Ibid., p. 196. 58. Alfred Russel Wallace, "Note on the Theory of Permanent and Geographical Varieties," Zoologist, 16 (1858), 5887-5888.

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Wallace, Darwin and the Theory of Natural Selection second part concerned the distinction between species and varieties, as he wrote to Bates in January 1858 [19]. This question still exists, of course, but the premises are entirely different. Then, species were real and permanent, "created" with certain relatively fixed characteristics; varieties, on the other hand, were produced by ordinary generation within strict limits of variation. Varieties were, if anything, an inconvenience, interfering with the rigid definition of species. Today, however, species have only a relative permanence; they also come about by ordinary generation, and varieties may (though they do not always) lead to the formation of new species. The definition of species has been a troublesome problem at least as far back as the time of Aristotle. Not until the time of the English naturalist John Ray (1628-1705) was the term limited to what we would today recognize as a breeding unit, including sex, color, and age variants. Ray concluded his discussion of species in his Historia Plantarum with the observation that "animals that differ in species preserve their distinct species permanently; one species never springs from the seed of another nor vice versa." 59 Linnaeus (1707-1778) was strongly influenced by Ray. A clear notion of what was meant by the term "species" was a necessity in organizing his Systema Naturae, first published in 1735. At first he was convinced of the permanence of species, but later, after he had become acquainted with the vast number of new forms brought home by explorers from all over the world, he was not so sure. Nevertheless, the belief in the creation of permanent species, which was closely intertwined with religion, was the generally accepted opinion in the first half of the nineteenth century, in spite of the heresies of people like Lamarck and Chambers. This vexed question had attracted Wallace's attention from the start, as can be seen from his early letters to Bates [3, 4]. It became a matter of daily concern when, as a collector, he was confronted over and over again with the task of properly identifying specimens. Unhampered by any strong religious convictions, he worried at the problem as a dog does a bone, as his "Notebook" attests. Lamarck had clearly grasped the gradual nature of change in species through time. Chambers, although he believed in evolution, thought that it proceeded by sudden leaps from species to species rather than by the accumulation of small changes. But Lyell stood on the opposite side of the fence, 59. Barbara G. Beddall, "Historical Notes on Avian Classification," Syst. Zool., 6 (1957), 134.

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firmly convinced of the fixity of species and of strict limitations to variation. Had either Chambers or Lyell been trained biologists or collectors, exposed day after day to the endless variations to be found in nature, they might have modified their views. But Wallace benefited from Lyell's position, using it as a springboard from which to develop his own. Although Lyell was unaware that he had been cast in the role of principal antagonist, his importance to Wallace cannot be overrated. It seems likely that the "Notebook" was intended as the basis of a projected book about which Wallace wrote to Darwin in the fall of 1857 and to Bates early in 1858 [16, 19].60 The entries of particular interest here were written between June 1855 (not long after the formulation of his "law") and November 1857, assuming that the dates scattered here and there are accurate indicators of the time and order of writing. They cover an assortment of topics relating to evolution-proofs of design, the theory of progressive development, transmutation and special creation, the "balance of species," geological changes and gaps in the fossil record, and the doctrine of the morphology of plants-and reflect Wallace's progress toward a solution of the problem of the origin of species.6' The argument from design was teleological, presuming that a contrivance existed in accordance with a preconceived plan. Adaptation between structure and function was recognized, but it was thought that a structure was provided simply because a function required it. Wallace wondered, however, how an animal could have necessities before it came into existence? And how could it "continue to exist unless its structure enabled it to obtain food?" 62 He thought that the arguments brought forward as proofs of design were absurd; not only were they insulting to the intelligence of a Supreme Being, but they also placed narrow limits on His power. Wallace returned several times to the inconsistencies in the geological record that made the theory of progressive development so troublesome for Lyell, observing that "the supposed contradictions all arise from considering it necessary that the highest forms of one group should appear before the lowest of the next succeeding, not considering that each group goes on 60. The information that Wallace's plan for his book is on the reverse side of the fragment about the jaguars was sent me by Sydney Smith. 61. Wallace, "Notebook," pp. 12-100. See also McKinney ("Wallace and Natural Selection," pp. 342-347), who has also pointed out that this is essentially a long argument with Lyell. 62. Wallace, "Notebook," p. 12.

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Wallace, Darwin and the Theory of Natural Selection progressing after other groups have branched from it." MLyell's static concept of species did not allow for such a dynamic interpretation. Were there connecting forms between groups, and if so, what were they? Wallace remarked that "as long as these most important characters [of groups] remain undiminished, no alterations of external form or habits can be held to shew any signs of a transition." 04 He questioned the popularly held transitional status of the seal, asking, "is not the Cetaceous group rather a modification of mammalia to an aquatic life than a link connecting them with fishes?"f5 He noted that neither the bat nor the hummingbird is a transition form either, because each contains the characteristic features of mammal or bird in a high state of development. The bat's wing is even less like a bird's wing than are less modified forelimbs of other mammals. Therefore, the highest forms of one group cannot be a transition to the lowest forms of the next. Lyell had also had trouble in accounting for the appearance of new species. Having decided in favor of the stability of species, he was obliged to settle for their extinction and "creation," admitting to only a limited amount of variation. Wallace was groping his way forward, however, questioning Lyell's assumptions: Lyell says that varieties of some species may differ more than other species do from each other without shaking our confidence in the reality of species-But why should we have that confidence? Is it not a nice prepossession or prejudice like that in favour of the stability of the earth which he has so ably argued against? In fact, what positive evidence have we that species only vary within certain limits? . . . we have no proof how the varieties of dogs were produced. All varieties we know of are produced at birth, the offspring differing from the parent. This offspring propagates its kind. Who can declare that it shall not produce a variety, which process continued at intervals will account for all the facts?66 Not only did Lyell believe that the amount of variation was strictly limited, but he also believed that it occurred over a brief period, after which no more changes took place no matter how long a time passed. Wallace thought that "Mr. Lyell must be very perplexed to know this." 67 Lvell did concede. 63. Ibid., p. 38. 64. Ibid., pp. 77-78; comma added. 65. Ibid., p. 76. 66. Ibid., pp. 39-40; commas added. See also Lyell, Geology, 4th ed., II, 435. 67. Wallace, "Notebook," p. 42.

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that time might bring about any metamorphosis, but only if such change were evidenced by a wholly new sense or organ. Wallace objected that "this would be taking a leap with a vengeance. We should have to get out of one class or order into another passing through many thousand species-If this is supposed to prove a change from one species to another, it can never be proved." 88 Lyell opposed Lamarck's theory of the transmutation of species, but Wallace defended his doctrine of their indefinite modifiability: Many of Lamarck's views are quite untenable & it is easy to controvert them, but not so the simple question of a species being produced in time from a closely allied distinct species, which, however, may of course continue to exist as long or longer than the offshoot. Changes which we bring about artificially in short periods may have a tendency to revert to the parent stock, though this in animals is not proved. This is considered a grand test of a variety. But when the change has been produced by Nature during a long series of generations, as gradual as the changes of Geology, it by no means follows that they may not be permanent, & thus true species produced.69 Wallace was to return later to the "grand test of a variety"; it became the opening gun in the essay he sent to Darwin from Ternate in February 1858. Lyell had made many contributions to the tangle of questions surrounding the geographical distribution of animals. But his a central problem-the "creation" of species-muddled conclusions, and Wallace put his finger on one of the inconsistencies to which this led: Lyell occupies much space in shewing how the species which are common to different & distant countries, might have been carried from one to the other by a variety of accidents. But this has never been felt to be a difficulty. The matter of wonder has always been that in distant countries of similar climate so many should be different. This he gets over by special creation of the species each in one spot as they are wanted. This is no doubt a very easy way of getting over it, but just as philosophical as to say that fossils of existing species 68. Ibid., p. 43; comma added. See also Lyell, Principles of Geology, 4th ed., II, 414. 69. Wallace, "Notebook," pp. 44 45; some commas added. See also note 100.

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Wallace, Darwin and the Theory of Natural Selection are remains of real animals while those which are not like any species now existing are special creations & not fossil

animalsat all.70 Wallace turned again to the peculiarities of distribution to be found on the Galapagos Islands. Lyell's theories were inadequate to the task of explaining them, as Wallace pointed out: In a small group of islands not very distant from the mai land, like the Galapagos, we find animals & plants different from those of any other country but resembling those of the nearest land. If they are special creations, why should they resemble those of the nearest land? Does not that fact point to an origin from that land? Again in these islands we find species peculiar to each island, & not one of them containing all the species found in the others as would be the case had one been peopled with new creations & the others left to become peopled by winds, currents, etc., from it. Here we must suppose special creations in each island of peculiar species though the islands are all exactly similar in structure, soil, & climate, & some of them within sight of each other, a work of supererogation one would suppose, as they must inevitably in time become peopled from each other, & contrary to what takes place elsewhere-Ireland is peopled from England. It may be said it is a mystery which we cannot explain, but do we not thus make unnecessary systems and difficulties by supposing special creations contrary to the present course of nature? For we must conclude the course of nature in peopling islands in the ocean to be uniform & that all islands distant from others should now be stocked with animals & plants equally peculiar. But we know this not to be the case. Volcanic islands recently produced & coral islands far in the ocean contai stragglers from the nearest land & no other, nothing peculiarl Now we can hardly suppose that islands would be left for ages to become stocked in this manner, & then the new & peculiar creations be introduced just when they were not wanted. According to Mr. Lyell's own arguments, they would hardly be able to hold their own against the previous occupiers of the soil & there would have to be a special extermination of them to make room for the new & peculiar species. We must therefore suppose that such islands as St. Helena & the Galapagos were stocked with their peculiar species 70. Ibid., pp. 45-46; 22-97.

see also Lyell, Principles of Geology, 4th ed., III,

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immediately on their being raised from the ocean, & they would then have a chance of keeping out the new comers which might be blown accidentally on their shores. This supposition will certainly explain the present condition of those islands but it has the disadvantage of being contrary to the present order of nature, for none of the islands which we have any reason to believe have been formed, since a very late geological era, are inhabited by peculiar species. They generally have not one species peculiar to themselves. On the other hand, islands which are thus peculiarly inhabited, appear to be of a considerable antiquity [in a marginal note, Wallace wrote, "this must be proved"].A long succession of generations appears therefore to have been requisite, to produce those peculiar productions found nowhere else but allied to those of the nearest land. The change like every other change in nature was no doubt gradual, & the suppositionthat other species were successively produced closely allied to those previously existing, & that while this was going on, the original or some of the first formed species died out, exactly accords with the facts as we find them & the process of peopling new islands at the present day.7' How far removed Lyell was from evolutionary theory is brought out at still another point. He thought that when climatic changes did cause the extinction of local species, any new inhabitants would be "perfectlydissimilar in their forms, habits, and organization."72 In other words, there would be a wholesale extinction followed by a renewal with altogether different species. Wallace pointed out, however, that the new species would more likely be modified forms of those previously existing: "It would be an extraordinarything if while the modificationsof the surface took [place] by natural causes now in operation, & the extinction of species was the natural result of the same causes, yet the reproduction& introduction of new species requiredspecial acts of creation, or some process which does not present itself in the ordinarycourse of nature." (At this point in his "Notebook,"Wallace inserted the followng note: "Introducethis and disprove all Lyell's arguments first at the commencement of my last chapter"-evidence that this was part of his proposedbook.)73 When environmental conditions changed, Lyell thought that new species already adapted to these new conditions would come in from surroundingareas before those in residence had 71. Wallace, "Notebook," pp. 46-49; some commas 72. Lyell, Principles of Geology, 4th ed., III, 154. 73. Wallace, "Notebook," pp. 50-51.

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Wallace, Darwin and the Theory of Natural Selection time to change (if they changed at all). Wallace agreed that "if the change took place rapidly, the exact results Lyell predicts might follow"; "but," he went on, 'how the same results could follow from an excessively gradual change it is impossible to understand." 74 Lyell and Lamarck both agreed that plenty of time was available, but they differed on what would happen. Lyell believed that species could change, but only to a limited degree and within the space of a few generations. Not only were they incapable of greater change, but such change would also be precluded by the immigration of other species already adapted to the new environment. Lamarck, on the other hand, believed that species did change gradually through time in response to changes in the environment, but his agency, the wills of the animals themselves, was suspect. Whatever their deficiencies (perhaps because of them), the beliefs of both these men were valuable steppingstones along Wallace's way. In the meantime, Wallace was reading as widely as circumstances permitted: Edward Blyth on the classification of varieties, Richard Owen on the varieties of color in man, and Leopold von Buch on the flora of the Canary Islands.75 Because von Buch's perceptive comments also influenced Darwin, Wallace's notes on them are worth quoting: On continents the individuals of one kind of plant disperse themselves very far, and by the difference of stations of nourishment & of soil produce varieties, which at such a distance not being crossed by other varieties & thus brought back to the primitive type, become at length permanent & distinct species. Then if by chance in other directions they meet with another variety equally changed in its march, the two have become very distinct species & are no longer susceptible of intermixture . . . He then shews that plants on the exposed peak of Teneriffe where they can meet & cross do not form varieties or species, while others such as Pyrethrum & Cineraria living in sheltered valleys & low grounds often have closely allied species confined to one valley or one island.7f 74. Ibid., p. 52; commas added. See also Lyell, Principles of Geology, 4th ed., III, 161-163. 75. Christian Leopold von Buch, Physicalische Beschreibung der Canarischen Inseln (Berlin: K. Akademie der Wissenschaften, 1825). An earlier report on the flora of the Canary Islands appeared in the Abhandlungen of the Society (1816-1817), 337-384. 76. Wallace, "Notebook," p. 90.

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Darwin in his own "Notebook"says, "VonBuch distinctly states that permanent varieties become species, pp. 147-150,-not being crossedwith others."77 Still anotherclue attractedWallace'sattention, and he asked: What is the importof the doctrineof Morphologyof plants? . . .For if stamens & petals & carpels have been in every case independently created as such, it is absurd to say they are modifications or developments of any thing else, & the absurdity is still greater if that of which they are said to be the development came into existence after them. In that case all the beautiful facts of morphology are a delusion & a snare, as much so as fossils would be were they really not the remains of living things but chance imitations of them. The natural inference of an unprejudiced person however would be that both are true records of the progress of the organic world. Nature seems to tell us that as organs are occasionallychanged &modifiednow, in individualplants, we may learn how the actual changes have taken place in the species of plants. A key is offered us to a mystery we could otherwise never have laid open, why should we refuse to use it?78 Sometime during these musings, Wallace wrote out his "Note on the Theory of Permanent and GeographicalVarieties,"following up an interest expressed many years earlier to Bates, and it was published early in 1858. Although he had been pondering a wide range of subjects, he limited the "Note"to showing the logical inconsistency in the suggestion that geographical varieties had permanent characters. If varieties differ from species only in the minuteness of the permanent characters, then the difference between them is merely a quantitative one and the dividing line becomes very difficult to distinguish. The only qualitativedifference that Wallace could discover was that of the pernanence vs. the impermanence of variations. But this was no better, for some groups so formed

were called special creations and others not. "Strangethat such widely different origins produce such identical results."79 If varieties are known to be produced by ordinary generation, why should species only slightly different be produced by special creation? "If there is no other character [than one of mere 77. Gavin de Beer, ed., "Darwin's Notebooks on Transmutation of Species," Bull. Brit. Mus. (Nat. Hist.), Hist. Ser., 2 (1960), 61. Darwin's first notebook was written between July 1837 and February 1838. 78. Wallace, "Notebook,"pp. 97-100. 79. Wallace, "Note," p. 5888. See also Appendix, 3.

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Wallace, Darwin and the Theory of Natural Selection degree of difference], that fact is one of the strongest arguments against the independent creation of species." 80 IV. AND DARWIN [Darwin] is now preparing for publication his great work on species and varieties, for which he has been collecting information twenty years. He may save me the trouble of writing the second part of my hypothesis by proving that there is no difference in nature between the origin of species and varieties, or he may give me trouble by arriving at another conclusion, but at all events his facts will be given me to work upon. Wallace to Bates, 4 January 1858, from Marchant, Alfred Russel Wallace

Eighteen hundred and fifty-eight was the year in which the careers of Wallace and Darwin collided. Wallace had initiated the correspondence between them when he wrote his first letter to Darwin in October 1856 [8].81 Why he wrote is not known; perhaps, as suggested earlier, he hoped that Darwin would be interested in his speculations on the Galapagos Islands puzzle. Although it was Wallace's third letter to Darwin that brought with it Wallace's discovery of the theory of natural selection, even this first one may have been disquieting. The contents of Wallace's letter can be partially surmised from Darwin's answer written in the following May [11]: the paper in the Annals, domestic versus wild varieties (a crucial point in the development of Wallace's ideas), hybrid sterility, and the effects of climatic changes. As to the paper, Darwin agreed "to the truth of almost every word"; he had, in fact, already pondered the same problems-classification, extinction and creation, and rudimentary organs-as can be seen from his own notebooks and his essay written in 1844. There was less agreement, however, on other subjects. Darwin later wrote Lyell (June 1858) that he and Wallace differed only in "that I was led to my views from what artificial selection has done for domestic animals [231." But they both made use of domesticated animals, although for different ends: Darwin to show that variation existed and could be channeled, Wallace to show that the usual definition of species, based on domesticated animals, did not apply to wild animals. (And, as Wallace wrote many years later, "it has always been considered a weakness in Darwin's work that he based his theory, primarily, on the evidence of variation in domesticated animals and cultivated plants.")82 Nor did Wallace and Darwin ever agree on the thorny problem of the sterility of hybrids. 80. Ibid., p. 5888. 81. See also Appendix, 69 and notes 43 and 162. 82. Alfred Russel Wallace, Dar-winism: An Exposition of the Theory of Natural Selection, with Some of its Applications (New York: Humboldt, 1889), p. iv.

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There was also a difference of opinion on the effect of climatic changes. In 1844 Darwin had written "thatprobablysuch changes of external conditions would, from acting on the reproductive system, cause the organization of the beings most affected to become, as under domestication, plastic."83 He had since modified his opinion, and in his letter to Wallace he agreed "on the little effect of 'climatal conditions."' Wallace, however, never did ascribe any such direct influence to climatic conditions in causing variations. Nevertheless, in spite of some disagreement it was plain, as Darwin said, that they had thoughtmuch alike. Darwin received Wallace's first letter late in April 1857. He was then deep in writing "his great work on species and varieties," having started almost exactly a year earlier at the urging of Lyell, with the strong support of the botanist Joseph Hooker [5, 6, 7]. As Lyell wrote not long afterward, "Part of the MS. of [Darwin's]projected work was read to Dr. Hooker as early as 1844, and some of the principal results were communicated to me on several occasions. Dr. Hooker and I had repeatedly urged him to publish without delay."84 It has recently been proposed,on evidence from Lyell's own notebooks, that it was actually Wallace'spaper in the Annals that prompted Lyell to reconsider the subject of species and to prod Darwin to publication, and, furthermore, that it was at this time that Darwinexplainedhis theoryto Lyell.88 Darwin had protested to Lyell that he did not like writing for priority, but had admitted that he "certainly should be vexed if any one were to publish my doctrines before me [5]"; and to his cousin, W. D. Fox, he had confided that he wished he "couldset less value on the bauble fame [10]."By 31 March 1857, he had completed six chapters of the projected work, and he may already have been at work on the seventh, comparing species and varieties, when Wallace's first letter arrived in late April. The coincidence in their thinking may have put Darwinon his guard. On 1 May 1857, Darwin wrote in answer (to some speculations by Wallace?) that he had been workingfor nearly twenty years "on the question how and in what way do species and varieties differ from each other [11]." He did not elaborate on 83. Darwin and Wallace, Evolution, p. 119. Text differs slightly from that in joint papers; see note 133. 84. Charles Lyell, The Geological Evidences of the Antiquity of Man, with Remarks on Theories of the Origin of Species by Variation, 1st ed.

(London: Murray, 1863), p. 408. 85. McKinney, "Wallace and Natural Selection," pp. 350-352.

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Wallace, Darwin and the Theory of Natural Selection the point, however, and left it up in the air. (Wallace had not yet written his own "Note" on the subject, and it is not known whether Darwin ever did see it.) As was his usual practice, Darwin included several requests for information, asking Wallace, among other things, to let him know "if you should, after receiving this, stumble on any curious domestic breed" of poultry.86 Perhaps as a result of this inquiry, Wallace made a few notes in his "Notebook," some time before November 1857, on unusual breeds of ducks.87 This small point will be brought up later in connection with Wallace's recollections of the beginning of his correspondence with Darwin. More important at the moment is Darwin's protestation that "it is really impossible to explain my views (in the compass of a letter) on the causes and means of variation in a state of nature." Was it really impossible? Two years earlier, in April 1855, Darwin had begun to correspond with the noted American botanist Asa Gray, whom he had once met briefly at Kew, and Gray had been providing him with many valuable comments. On 20 July 1857, not long after receiving his first letter from Wallace, Darwin wrote again to Gray, saying, "I should like to tell you (and I do not think I have) how I view my work," condensing into a few sentences the gist of his theory [12].88 A recent biographer of Gray suggests that Darwin felt it necessary to let Gray in on his secret to ensure the continuance of this useful correspondence, but this does not seem to be a necessary assumption.89 More to the point, Darwin seemed rather to fear that Gray would despise him and his crotchets, and in his next letter (5 September) he confessed that he had been afraid that Gray might think him "worth no more notice or assistance" because of his unorthodox views [14].90 (Even in March 1860 Darwin considered Gray to be a convert to his views only "to some extent."))91 Along with this answer to Gray, Darwin sent a copy of an outline that he had made of his theory, "as you seem interested in the subject." This is the famous extract published the fol86. The paragraph containing this request is published in Marchant, Wallace, p. 108, but it was omitted from the Darwin, Life and Letters, I, 454. See also note 87. 87. Wallace, "Notebook," p. 91. See also Appendix, 69, Marchant, Wallace, p. 86, and notes 161 and 162. 88. See also note 146. 89. A. Hunter Dupree, Asa Gray, 1810-1888 (Cambridge: Harvard University Press, 1959), p. 244. 90. See also note 146. 91. Darwin, Life and Letters, II, 87.

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lowing year as part of the Darwin-Wallace joint papers. Darwin concluded his letter to Gray with the following request: You will, perhaps, think it paltry in me, when I ask you not to mention my doctrine; the reason is, if any one, like the author of the 'Vestiges,'were to hear of them, he might easily work them in, and then I should have to quote from a work perhaps despised by naturalists, and this would greatly injure any chance of my views being received by those alone whose opinionI value [14]192 Why did Darwin send this statement to Gray, who responded that it was "grievouslyhypothetical [15, 17]" rather than to Wallace (who was hardly at this time, however, a scientific peer), who would have understood?Was it Wallace rather than Chambers of whom he was afraid? If so, a recent outline of his views, including the important addition on divergence, mailed to the eminent American botanist might protect his ideas. And, whatever his intentions may have been, this indeed was the result. Finally, on 29 November 1857, Darwin thanked Gray for his help, remarking that "every criticism from a good man is of value to me [17]."93 But the subject was apparently not pursued, and this concludes the series of letters about Darwin's theory. Wallace was "much gratified"by Darwin's first letter, as he wrote Bates in January 1858, but he was no wiser than before (had he asked?) about Darwin's opinion for or against a "difference in nature between the origin of species and varieties [19]." 94 In any case, he had pretty wel made up his own mind already. Judging from Darwin's next answer, Wallace in reply once again brought up his paper in the Annals and also remarked on various problems relating to the geographical distribution of animals. But the only piece on Wallace's side of this early correspondencethat is still in existence is a snippet from his answering letter of 27 September 1857, on the breeding habits of jaguars and his plan for his book [16].9rFor the rest, Wal92. This paragraph has been variously interpreted; see Dupree, Asa Gray, p. 246 and Himmelfarb, Darwin, p. 207. 93. See note 146. 94. See also Loren Eiseley, Darwin's Century and the Men Who Discovered It (Garden City, N.Y.: Doubleday, 1958), p. 291, where he considers this correspondence "stimulating" to Wallace. But Wallace received no such positive statement as was given to Gray. 95. Unpublished fragment in the Cambridge University Library; see also note 60. For Darwin's methods of filing his letters, see notes 140-143.

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Wallace, Darwin and the Theory of Natural Selection lace's opinions must be conjectured from Darwin's letters to him. By the time Darwin answered Wallace's second letter on 22 December 1857, he had almost completed the ninth chapter of his book, this one on hybridism. He assured Wallace that his paper had not gone unnoticed, Lyell and the zoologist Edward Blyth having called it to his attention; none of these men, however, had bothered to write Wallace about it. Darwin passed up his second and last opportunity to tell Wallace about his theory, saying that "though agreeing with you on your conclusions in that paper, I believe I go much further than you; but it is too long a subject to enter on my speculative notions [18]." It seems unlikely, however, that Wallace received this letter before the end of February 1858; most of the letters exchanged by the two men took anywhere from three to six months to reach the recipient. In the meantime, in his January 1858 letter to Bates, Wallace told him of his plans, explaining that "I have prepared the plan and written portions of an extensive work embracing the subject in all its bearings and endeavouring to prove what in the paper [in the Annals] I only indicated." He did not seem to be overly concemed about Darwin's conclusion on the origin of species and varieties, remarking that Darwin might save him the trouble of proving that there was no difference in their nature [19]. It has been claimed that Wallace, "duly warned off" by Darwin's first letter, had nevertheless continued his own work on the subject.96 It should be objected that this was no private preserve of Darwin's. Many people were interested in it, as Wallace was well aware. Darwin gave Wallace no hint of a solution to the problem; why should he not continue with what had been a consuming interest for many years? Bates himself, on his return home, wrote that one of their purposes in going to the Amazon was to "gather facts, as Mr. Wallace expressed it in one of his letters, 'towards solving the problem of the origin of species,' a subject on which we had conversed and corresponded much together."97 If Darwin had been working on the problem for twenty years, Wallace had been working on it for at least ten, the major difference being that Darwin had long had a theory against which he was collecting facts, while Wallace was still actively searching for one. By now Wallace had concluded that there was no qualitative difference in the origin of species and varieties and that they 96. Himmelfarb, Darwin, p. 236. 97. Bates, The Naturalist, p. iii; see also Appendix, 4 and note 17.

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were formed gradually by natural means with a relationship in space and time to what had gone before, but without any necessary progression. Only a short distance separated him from his goal, a "'theoryof the origin of species." In February 1858 the final step was taken. Wallace was lying ill in Ternate in the Moluccas, mulling as usual over his problem, when at last he found the key to the puzzle: the theory of natural selection. Much has been made of the fact that the solution came to him while he was ill but, as he impatiently remarked later, he "had no idea whatever of 'dying,' -as it was not a serious illness [69]." Indeed, he had frequently been sick, and sometimes much sicker. Although not identified at the time, the disease has recently been referred to as malaria.98 As soon as he was able, Wallace wrote out his theory with the title, "On the Tendency of Varieties to depart indefinitely from the Original Type," and sent it to Darwin with the request that it be shown to Lyell.99 Had he chosen any other recipient, the results would have been different. Gray's response to Darwin's disclosure, for instance, had been that it was too hypothetical. But to Darwin, Wallace's paper was little short of a calamity. In his "Note," Wallace had been struggling with the supposed distinction between permanent varieties and permanently invariable species. Now he saw his way clear. Belief in variation within strict limits and reversion to the original type was based on domestic animals and then applied to wild animals. But domestic animals are artificial and unable to maintain themselves without the help of man. If allowed to go wild, they must either return to something similar to the original type or become extinct. Wild animals, on the other hand, must be adapted to their environment. Their every faculty is constantly exercised in keeping themselves alive. Any improvement in organization is quickly taken advantage of, and a new variety is thus superior to its predecessor. Being superior, it "could not return to the original form; for that form is an inferior one, and could never compete with it for existence." 100 Quite the opposite is true of domestic animals, which are inferior from the point of view of maintaining themselves in the wild. Thus varieties in nature tend to depart indefinitely from the original tvDe. 98. Julian S. Huxley and H. B. D. Kettlewell, Charles Darwin and his World (New York: Viking Press, 1965), p. 74. 99. Alfred Russel Wallace, "On the Tendency of Varieties to depart indefinitely from the Original Type," J. Linn. Soc. London (Zool.), 3 100. Ibid., p. 58. See also note 69. (1858), 53-62.

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Wallace, Darwin and the Theory of Natural Selection Several years earlier, Wallace had found puzzling Lyell's belief that the balance of species was preserved by plants, insects, mammals, and birds adapted to the purpose, and he had worried over this problem in his "Notebook": This phrase is utterly without meaning. Some species are very rare, others very abundant-where is the balance? Some species exclude all others in particular tracts-where is the balance-When the locust devastates vast regions, & causes the death of animals & man, what is the meaning of saying the balance is preserved . . . To human apprehension there is no balance but a struggle in which one often exterminates the other-When animals and plants become extinct, where is the balance. If any state can be imagined proving a want of balance, then a balance may perhaps be admitted, but what state is that?10' Now, two years later, Wallace had his answer. In the "struggle for existence," many individuals must perish annually. Even the least fecund species would soon overrun the earth if its numbers went unchecked. Those that survive are the ones best adapted to obtain food and to withstand their enemies and the seasonal changes in the weather; those that die are the young, the old, and the sick. In applying this not only to individuals but also to species, Wallace thought he had an answer to why some species are rare while others are abundant. Besides this, the animal population of a country cannot increase materially if conditions remain the same. In the "struggle for existence," therefore, those individuals and species best adapted to maintain themselves survive. It is well known that Wallace and Darwin both read Malthus' famous Essay on the Principle of Population, Wallace before leaving Leicester and Darwin after returning home from his voyage. Malthus' interest was in the moral perfectibility of man, and it was in this light that he discussed the checks to population growth-famine, war, disease, and vice-but Wallace and Darwin were both impressed by the implications of these checks. The exact extent of Malthus' influence is hard to determine and has been the subject of much debate, but at the least his forceful presentation was widely known. Darwin read Malthus in the fall of 1838. There is no indication of this in the first edition of his Voyage of the Beagle, 101. Wallace, "Notebook," pp. 49-50; some commas added. See also Lyell, Principles of Geology, 4th ed., III, 98-120, where he discusses the "checks and counter-checks which nature has appointed to preserve the balance of power amongst species."

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however, because though published in 1839, the writing of it was largely finished by June 1837. Darwin had tried vainly to account for the extinction of so many peculiar South American forms that were related to the present inhabitants, concluding only that: On such grounds it does not seem a necessary conclusion, that the extinction of species, more than their creation, should exclusively depend on the nature (altered by physical changes) of their country. All that at present can be said with certainty, is that, as with the individual, so with the species, the hour of life has run its course, and is spent.102 This comment was greatly enlarged for the second edition (1845) and clearly shows the influence of Malthus: Nevertheless, if we consider the subject under another point of view, it will appear less perplexing. We do not steadily bear in mind, how profoundly ignorant we are of the conditions of existence of every animal; nor do we always remember, that some check is constantly preventing the too rapid increase of every organized being left in a state of nature. The supply of food, on an average, remains constant; yet the tendency in every animal to increase by propagation is geometrical; and its surprising effects have nowhere been more astonishingly shown, than in the case of the European animals run wild during the last few centuries in America. Every animal in a state of nature regularly breeds; yet in a species long established, any great increase in numbers is obviously impossible, and must be checked by some means. We are, nevertheless, seldom able with certainty to tell in any given species, at what period of life, or at what period of the year, or whether only at long intervals, the check falls; or, again, what is the precise nature of the check. Hence probably it is, that we feel so little surprise at one, of two species closely allied in habits, being rare and the other abundant in the same district; or, again, that one should be abundant in one district, and another, filling the same place in the economy of nature, should be abundant in a neighboring district, differing very little in its conditions. If asked how this is, one immediately replies that it is determined by some slight difference in climate, food, or the number of enemies: yet how rarely, if ever, we can point out the precise cause and manner of action of the check I We are, therefore, driven to the conclusion, that 102. Darwin, Voyage of the Beagle (1839),

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p. 212.

Wallace, Darwin and the Theory of Natural Selection causes generally quite inappreciable by us, determine whether a given species shall be abundant or scanty in numbers. . . .If then, as appears probable, species first become rare and then extinct-if the too rapid increase of every species, even the most favoured, is steadily checked, as we must admit, though how and when it is hard to say-and if we see, without the smallest surprise, though unable to assign the precise reason, one species abundant and another closely-allied species rare in the same district-why should we feel such great astonishment at the rarity being carried a step further to extinction?103 Wallace did not have Malthus with him, but he did have Darwin. Familiar as he already was with the Malthusian arguments, he must have noticed their inclusion in the second edition of the Voyage of the Beagle. These principles, first suggested in 1798, were now used by Wallace and Darwin in a rather different context. But Malthus alone was not enough. As Wallace justly pointed out many years later, "along with Malthus I had read, and been even more deeply impressed by, Sir Charles Lyell's immortal 'Principles of Geology.'" 104 The final and most important point of Wallace's paper was the application of the concepts he had developed to varieties. Even slight variations would have an effect, either favorable or unfavorable, and under changed physical conditions a betteradapted variety might survive its parent species. (This would be true only of wild varieties, however, for domesticated animals turned wild are rarely able to maintain themselves.) This process repeated would lead to "progression and continued divergence." 105 At last Wallace had a mechanism that explained the knotty problem of progression which had so baffled Lyell, and the equally puzzling problem of divergence; and it could also replace Lamarck's generally discredited theory that progressive changes were due to the wills of the animals themselves. Darwin's approach was a little different. Because Wallace is the focus of this study, discussion here will be limited to the two selections from Darwin's writings that became part of the joint papers in 1858. The first was an extract from an essay written in 1844.106 Darwin had remarked there that De Can103. Ibid., (1845), pp. 174-176. 104. Linnean Society of London, The Darwin-Wallace Celebration, p. 118. 105. Wallace, "On the Tendency," p. 59. See also note 37. 106. Charles Darwin, "Extract from an Unpublished Work on Species, by C. Darwin, Esq., consisting of a portion of a Chapter entitled 'On the

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dolle's war of nature "is the doctrine of Malthus applied in most cases with ten-fold force" 107 (he was to use a similar phrase in the Origin of Species).108 Under these circumstances, slight variations caused directly by changed physical conditions might lead to small improvements in organisms through the natural selection of those better adapted.109 Darwin also discussed sexual selection, another subject on which he and Wallace were to differ strongly. The brief abstract enclosed with the letter to Asa Gray summarized Darwin's conclusions at this later date, 1857.110 Selection of variations by man is recognized in the propagation of domestic animals. Physical conditions are known to have changed over a great length of time. These changed conditions have caused variations to occur in organisms in a state of nature, although Darwin was no longer certain that this was the sole cause. Finally, there is a natural power comparable to that of man which selects those that survive in the struggle for life, a power which Darwin called Natural Selection. In a country undergoing changes, these slight variations would be selected and gradually accumulated, leading to new varieties adapted to the new conditions. At the end, Darwin added a paragraph on his principle of divergence. The solution to this problem-"that the varying offspring of each species will try (only few will succeed) to seize on as many and as diverse places in the economy of nature as possible" "'-had not occured to him until 1852,112 'long after I had come to Down," 113 and so was not yet a part of a formal statement of his views. He knew from Wallace's paper in the Annals that he too was trying to solve this problem. Variation of Organic Beings in a state of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and true Species,'" J. Linn. Soc. London (Zool.), 3 (1858), 46-50. See also note 133. 107. Ibid., p. 47. 108. Charles Darwin, On the Origin of Species by Means of Natural Selection, or the Preservation of favoured Races in the Struggle for Life (London: Murray, 1859; facsimile reprint, Cambridge: Harvard University Press, 1964), p. 63. 109. See also note 83. 110. Charles Darwin, "Abstract of a Letter from C. Darwin, Esq., to Prof. Asa Gray, Boston, U.S., dated Down, September 5th, 1857," J. Linn. Soc. London (Zool.), 3 (1858), 50-53. See also Appendix, 14 and notes 88-93. 111. Ibid., pp. 52-53. See also note 37. 112. Gavin de Beer, Charles Darwin: a Scientific Biography (Garden City, N.Y.: Doubleday, 1964), p. 140. 113. Darwin, Life and Letters, I, 69.

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Wallace, Darwin and the Theory of Natural Selection V. THE JOINT PAPERS I was not aware before that your father had been so distressed-or rather disturbed-by my sending him my essay from Ternate. Wallace to Francis Darwin, 20 November

1887

"June 14th Pigeons (interrupted)." 114 Such is the cryptic note in Darwin's "Journal" indicating the receipt of Wallace's paper on 18 June 1858. By this time he had completed twelve chapters of his book and was at work on the thirteenth, and his distress at being thus forestalled can easily be imagined. The story of this most dramatic moment has often been recounted. But, as Hooker observed, the details stem entirely from some of the letters written at the time by Darwin to himself and to Lyell [22-26, 29, 33-36];115 all other documentary evidence, the letters from Wallace, Lyell, and Hooker to Darwin, as well as the manuscript of Wallace's paper, has disappeared. The facts, consequently, are difficult to determine, and the circumstances have been variously interpreted. There is no way of ascertaining exactly why Wallace sent his paper to Darwin; certainly he could not have anticipated the result. With no hint from Darwin, he could not have realized that he had stumbled onto the very foundation of Darwin's work. Darwin, on the other hand, must have had a fair notion of Wallace's progress from his published papers and perhaps a warning of this disaster from his letters, the first of which may indeed have precipitated the sketch sent to Gray. Wallace, who had been away from England for many years, was a self-educated collector from outside the regular establishment, and he had few personal contacts among the scientific elite. By dint of his own efforts, he had finally established a correspondence with one of its members, Charles Darwin. He may well have hoped for some useful criticism from Darwin and Lyell, but he could hardly have expected to be catapulted into the front ranks himself. From the evidence, it appears that Wallace sent his paper to Darwin with the request that it be forwarded to Lyell, "should he think it sufficiently novel and interesting [20]." 11I Darwin's own letter to Lyell, written on 18 June, said only 114. Gavin de Beer, ed., "Darwin's Journal," Bull. Brit. Mus. (Nat. Hist.), Hist. Ser., 2 (1959), 14. 14 June 1858 was the day on which Darwin began this chapter. 115. See also note 139. 116. Charles Lyell and Joseph D. Hooker, "[Letter communicating the Darwin-Wallace Papers to the Linnean Society]," 30 June 1858, J. Linn. Soc. London (Zool.), 3 (1858), 46.

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that Wallace "has to-day sent me the enclosed, and asked me to forward it to you [22]."Lyell's recollection later was that the paper had been brought to him by Hooker, who then suggested some sort of joint publication.117In Leonard Huxley's biography of Hooker, it is stated that Darwin "had first confided Wallace's unexpected letter" to him, and that he first suggested joint publication and also the getting of Lyell's opinion.118Whatever the precise details, Hooker, Darwin's "most intimate friend," accepted the larger share of the responsibilityfor what happened. Darwin was now in a dilemma: "He does not say he wishes me to publish, but I shall, of course, at once write and offer to send to any journal. So all my originality, whatever it may amount to, will be smashed [22]." In fact, Darwin did start a letter to Wallace giving up his claims to priority, but he never finished it, for his old friends, Hooker and Lyell, suggested a compromise.If Darwin'sand Wallace'sroles had been reversed, as they could have been, Wallace would have had no one to help him resolve the difficulty. A week later, on 25 and 26 June, Darwin wrote Lyell again. A joint publicationof some kind had apparentlybeen proposed, although "Wallace says nothing about publication" and Darwin was properly hesitant about the proprieties involved. He mentioned a copy of his sketch sent to Gray "about a year ago . . . (owing to correspondence on several points)." ("Cor-

respondence"here probably means actual letter-writingrather than agreement, because the sketch "gives most imperfectly only the means of change," a subject new to Gray.) He also enclosed the letter from Wallace and requested that Lyell get Hooker's opinion; some of the confusion on this point has already been mentioned [20, 23, 24, 26]. By 29 June, Darwin had their answers. He was to send to Hooker both Wallace's paper (which Lyell must alreadyhave returnedto him) and his own sketch sent to Asa Gray. Although they had apparently not asked for it, he also sent along his much more extensive sketch (230 pages), written in 1844, to show by notes in Hooker's handwriting that he had read it [25, 26].119

Darwin's letters were usually written with an intensity of feeling lacking in the more pedestrian efforts of many of his contemporaries.At this moment they were shrill with anxiety and doubt. But Darwin was being sorely tried. He was troubled not only by Wallace's communicationbut also by severe illness 117. Lyell, Principles of Geology, 10th ed., II, 278. 118. Leonard Huxley, ed., Life and Letters of Sir Joseph Dalton Hooker 119. See also note 84. (London: Murray, 1918), II, 465.

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Wallace, Darwin and the Theory of Natural Selection in his family. An infant son died of scarlet fever on 28 June, and a daughter was seriously ill with diphtheria. Finding a suitable forum for the papers at this time of year would ordinarily have presented still another problem. But both Hooker and Lyell, as Fellows of the Linnean Society of London, knew that one had unexpectedly become available. Robert Brown, a leading botanist, former President and then Council Member of the Society, had died on 10 June. Out of respect, the last meeting of the old session, held on 17 June, was adjourned before the reading of the scheduled papers. But Brown had to be replaced on the Council within three months, and, as the new session would not start until November, it was decided to hold the extra meeting on 1 July. Without consulting anyone else, Hooker and Lyell transmitted their selections to the Secretary of the Society on 30 June, to be read by him the next day. As Hooker said in 1908: It cannot fail to be noticed that all these inter-communications between Mr. Darwin, Sir Charles Lyell, and myself were conducted by correspondence, no two of us having met in the interval between June the 18th and July the 1st, when I met Lyell at the evening meeting of the Linnean Society; and no fourth individual had any cognisance of our proceedings.120 This was not an occasion of "mutual nobility," 121 nor was it "a monument to the natural generosity of both the great biologists," 122 as is so often claimed. It was clearly not mutual because Wallace's paper was read without his knowledge or consent, and he knew nothing about it until October. Nor does it seem to have been particularly noble. However just Darwin's claims to priority, he was a gainer, not a loser, from the decision. Wallace had no opportunity to be either noble or generous. Wallace, "a gentleman attached to the study of Natural History," was not unknown to the Linnean Society. The first two volumes of the Society's Journal (Zoology) were largely taken up with descriptions (written by others) of the collections of insects he had sent home from Singapore, Malacca, and Sarawak. The Society was later to publish some of Wallace's most 120. Linnean Society of London, The Darwin-Wallace Celebration, p. 15. This and the information of Brown (Ibid., pp. 14-15) were omitted in Marchant, Wallace, p. 98. 121. Eiseley, Darwin's Century, p. 292. 122. Julian S. Huxley, "Alfred Russel Wallace," Dictionary of National Biography, Supplement 1912-1921 (London: Oxford University Press, 1927), p. 547.

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important papers, but he himself was not elected a Fellow until 1872. Darwin, on the other hand, was already a Fellow, and had just been elected to the Council in May. Some thirty people, perhaps more, out of a membership of over four hundred were present at the meeting. Although some of their names might not be recognized today, fully half of those listed in the Minutes as attending have rated notices in Britain's renowned Dictionary of National Biography, certainly a distinguished audience.123 The evening was a full one. The business of the meeting was transacted, and then came the reading of the papers, the joint papers by Darwin and Wallace followed by five of the six previously scheduled for 17 June. The joint papers were introduced by a letter from Lyell and Hooker explaining what they had done and why. The first selection was from Darwin's essay of 1844, an "Extract from an unpublished Work on Species, by C. Darwin, Esq., consisting of a portion of a Chapter entitled 'On the Variation of Organic Beings in a state of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and true Species."' Darwin appended to the published version a note that "this MS. work was never intended for publication, and therefore was not written with care." This was no hastily written summary, however, for Darwin had had it copied and bound, and he had also left instructions to his wife for its publication in the event of his premature death.124 Secondly came the "Abstract of a Letter from C. Darwin, 123. Listed in the minutes of the meeting, in the Society's DarwinWallace Celebration, pp. 81-86. The following can be found in the D.N.B.: botanist; Baird, William (1803-1872), zoologist; Ball, John (1818-1889), Baly, William (1814-1861), physician (visitor); Bell, Thomas (17921880), dental surgeon and zoologist (President); Bennett, John Joseph (1801-1876), botanist (Sole Secretary), not listed as present, although botanist; he presumably read the papers; Bentham, George (1800-1884), explorer and naturalist; Busk, Burchell, William John (1782?-1863), George (1807-1886), physician and scientist (Under- (Zoological) Secretary), not listed as present, although Hooker later recalled that he was; naturalist and physician; Carpenter, William Benjamin (1813-1885), Currey, Frederick (1819-1881), mycologist; Fitton, William (1780-1861), botanist; Hooker, physician and geologist; Henfrey, Arthur (1819-1859), botanist; Lyell, Charles (1797-1875), geolJoseph Dalton (1817-1911), geologist; Seeman, Berthold ogist; Salter, John William (1820-1869), botanist and traveler; Ward, Nathaniel Bagshaw Carl (1825-1871), (1791-1868), botanist and physician. Others may have been present as the list ends with "etc., etc." 124. The date is incorrectly given as 1842 in the published papers. Darwin further confused the issue by using the date 1839 in a letter to Wallace; see Appendix, 43. For details of Darwin's plans, see Himmelfarb, Darwin, pp. 190-191.

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Wallace, Darwin and the Theory of Natural Selection Esq., to Prof. Asa Gray, Boston, U.S., dated Down, September 5th, 1857," the outline of his theory of natural selection that Darwin had sent to Gray. Francis Darwin was later of the opinion that the reason for the inclusion of this note was the discussion of the "principle of divergence," an important part of Darwin's theory not included in the 1844 essay.125 Hooker was aware that Darwin gave divergence equal prominence with natural selection as "the keystone of my book [21]," although he apparently did not understand the connection between them. In his own essay, "On the Flora of Australia," published at almost the same time as Darwin's Origin of Species, Hooker wrote that "the tendency of varieties, both in nature and under cultivation, when further varying, is rather to depart more and more widely from the original type than to revert to it." 126 Darwin objected that this was "without selection doubtful." 127 Third and last was Wallace's paper, "On the Tendency of Varieties to depart indefinitely from the Original Type." But no note was added to indicate that Wallace had not written for publication either. It was Hooker's recollection twenty-eight years later (whether accurately or no; certainly public reaction to the publication of the papers was almost nil) that the interest was intense, although there was no discussion. Thomas Bell, the President, though a personal friend of Darwin's, "was hostile to the end of his life." Neither of the Secretaries, George Busk and John J. Bennett, said anything, nor did the botanist George Bentham [67]. (Thomas Huxley, later to be "Darwin's bulldog," was not present, not being elected a Fellow until December 1858.) Bentham may have been silent, but his feelings were those of "severe pain and disappointment." His was the only one of the six previously scheduled papers that was not read. Many years later he recalled the events in a letter to Francis Darwin: On the day that his [C. Darwin's] celebrated paper was read at the Linnean Society, July 1st, 1858, a long paper of mine had been set down for reading, in which, in commenting on the British Flora, I had collected a number of observations and facts illustrating what I then believed to be a fixity in species, however difficult it might be to assign their limits, and showing a tendency of abnormal forms produced by cultivation or otherwise, to withdraw within those orig125. Darwin and Wallace, Evolution, p. 34. See also note 37. 126. Quoted in Francis Darwin, ed., More Letters of Charles Darwin: a Record of his Work in a Series of Hitherto Unpublished Letters (New York: Appleton, 1903), I, 134. 127. Ibid.

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inal limits when left to themselves. Most fortunately my paper had to give way to Mr. Darwin's and when once that was read, I felt bound to defer mine for reconsideration; I began to entertain doubts on the subject, and on the appearance of the 'Origin of Species,' I was forced, however reluctantly, to give up my long-cherished convictions, the results of much labour and study, and I cancelled all that part of my paper which urged original fixity, and published only portions of the remainder in another form, chiefly in the 'Natural History Review.' I have since acknowledged on various occasions my full adoption of Mr. Darwin's views, and chiefly in my Presidential Address of 1863 [to the Linnean Society], and in my thirteenth and last address, issued in the form of a report to the British Association at its meeting at Belfast in 1874 [66]. Bentham had not given in easily; even in his Presidential Address in 1862 he was still struggling against the new doctrine: I do not refer to those speculations on the origin of species, which have excited so much controversy; for the discussion of that question, when considered only with reference to the comparative plausibility of opposite hypothesis, is beyond the province of our Society. Attempts to bring it forward at our meetings were very judiciously checked by my predecessor [Bell] in this Chair, and I certainly should be sorry to see our time taken up by theoretical arguments not accompanied by the disclosure of new facts or observations.128 Bell was a dental surgeon and zoologist, but "as a naturalist he was more at home in his study than in the field, and he made few original contributions of special value to zoology. As a writer, his chief merit is that of agreeable compilation." 129 In his own Presidential Address in 1859, he dismissed the joint papers altogether: The year which has passed . . . has not been unproductive in contributions of interest and value, in those sciences to which we are professedly more particularly addicted, as well as in every other walk of scientific research. It has not, indeed, been marked by any of those striking discoveries which at once revolutionize, so to speak, the department of 128. Proc. Linn. Soc. London (1 November 1860-19 Lxcxi. 129. G. T. Bettany, "Thomas Bell," D.N.B., II, 175.

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June 1862),

p.

Wallace, Darwin and the Theory of Natural Selection science on which they bear; it is only at remote intervals that we can reasonably expect any sudden and brilliant innovation which shall produce a marked and permanent impress on the character of any branch of knowledge, or confer a lasting and important service on mankind. A Bacon or a Newton, an Oersted or a Wheatstone, a Davy or a Daguerre, is an occasional phenomenon, whose existence and career seem to be especially appointed by Providence, for the purpose of effecting some great important change in the condition or pursuits of man.130 Darwin's immediate reaction to Wallace's paper was, humanly enough, great distress, followed by relief at the solution worked out by Hooker and Lyell. "But," he wrote to Hooker, "in truth it shames me that you should have lost time on a mere point of priority." (If it was not a point of priority, what, indeed, was the hurry?) Although he was not yet clear on exactly which of his papers had been read at the Linnean Society meeting, he was glad that Hooker planned to write Wallace about the affair, "as it would quite exonerate me [29]." Darwin was "more than satisfied" when he discovered what had been done: the strictly chronological (and alphabetical) arrangement of the papers meant that his preceded Wallace's (as does his name in the references to the published papers), when "I had thought that your letter and mine to Asa Gray were to be only an appendix to Wallace's paper [33]." 131 On 13 July Hooker and Darwin both sent letters to Wallace explaining the turn of events [31, 32]. Unhappily, these letters are missing, although Wallace carefully saved most of Darwin's letters to him (and it is from them that we know of Wallace's early letters to Darwin). A few days later Darwin also thanked Lyell for his part, again expressing himself as "far more than satisfied [34]." He was pleased to have the public backing of men like Lyell and Hooker. It was only after some years of struggle, however, that Lyell became a "convert," while Hooker, although convinced of the action of natural selection, nevertheless vacillated on its importance. Even Darwin hedged as time went on. Of the four men, Wallace was to be the most steadfast, maintaining to the end his belief in "the overwhelm130. J. Linn. Soc. London (Zool.), 4 (1859), viii-ix. 131. The collective title for the joint papers and the accompanying letter is entered as follows: Charles Darwin and Alfred Russel Wallace, "On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection," J. Linn. Soc. London (Zool.), 3 (1858), 45-62.

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ing importance of Natural Selection over all other agencies in the production of new species." 132 By 20 July Darwin had received the proof sheets, and he returned them to Hooker the next day, with "only a few corrections in the style [351." In fact, judging from the original texts as published in Evolution by Natural Selection and the Life and Letters of Charles Darwin, several hundred changes were made in both the 1844 sketch and the letter to Asa Gray, not only in the punctuation and wording but even in whole phrases.133 To have been scrupulously fair, it would seem that no changes should have been made at all. Darwin complained to Hooker that he had not been writing for publication [36], and a note to this effect was inserted in the Journal, as already mentioned. Wallace did not have these opportunities. It is not known who read the proof of his paper nor what became of his manuscript. In later reprintings he added phrases in footnotes that he would have inserted in the text, but he made no corrections then because of the historical importance of the document.134 The joint papers were published on 20 August 1858 in No. 9 of the third volume of the Linnean Society's Journal (Zoology). The sudden confrontation with Darwin threw Wallace into the limelight. But he had not stumbled upon the theory of natural selection by accident; he was to be neither a hanger-on nor a blind follower of Darwin's, and he was to make many valuable and original contributions of his own to evolutionary theory. His interests often paralleled those of Darwin, but his point of view frequently differed. Because of Darwin's illness and isolation at Down, their long and fruitful association is recorded in a correspondence that continued until Darwin's death.135 Wallace's first intimation of what had happened came when 132. Wallace, Darwinism, p. iv. 133. Compare the text of the joint papers with the 1844 excerpt in Darwin and Wallace, Evolution, pp. 116-121, and the letter to Asa Gray in Darwin, Life and Letters, I, 479-482. See also notes 83, 138, 150, and 158. 134. Wallace added two footnotes in the first reprinting in his Contributions to the Theory of Natural Selection (London: Macmillan, 1870); he omitted these and added a third in the second reprinting in Natural Selection and Tropical Nature (London: Macmillan, 1891), p. 27n, with the comment that "it must be remembered that the writer had no opportunity of correcting the proofs of this paper." 135. The complete extant correspondence is in Marchant, Wallace, pp. 107-262. The texts differ somewhat from those in Darwin, Life and Letters, besides the publication of sections omitted there. See also note 158.

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Wallace, Darwin and the Theory of Natural Selection he received the letters from Hooker and Darwin in early October 1858. At last he had aroused attention-attention that assured him, as he wrote his mother, "the acquaintance and assistance of these eminent men" on his return home. Whatever else Darwin's letter conveyed to Wallace, it was not the pain and anguish of those two final weeks in June. Wallace, unaware of the flurry he had aroused, told his mother that he was "highly gratified . . . I sent Mr. Darwin an essay on a subject on which he is now writing a great work. He showed it to Dr. Hooker and Sir C. Lyell, who thought so highly of it that they immediately read it before the Linnean Society [37]." And to an old boyhood friend, George Silk, Wallace crowed: "if you have any acquaintance who is a fellow of the Linnean Society, borrow the Journal of Proceedings for August last, and in the last article you will find some of my latest lucubrations, and also some complimentary remarks thereon by Sir Charles Lyell and Dr. Hooker, which (as I know neither of them) I am a little proud of [421." Almost thirty years passed before Wallace learned some of the details of Darwin's side of the story. Darwin, who received Wallace's answering letter in January 1859, was "extremely much pleased" with it; he had been "anxious to hear what your impression would be." He incorrectly referred to his own extracts as having been written in 1839, when in fact the first was written in 1844 and the second, the letter to Asa Gray, had been written in 1857, only a year and a half before [38, 43]. By November 1858 Wallace had received a copy of the Journal containing the papers and could read for himself Darwin's "distinct and tangible idea." The tenor of Wallace's comments can be judged from Darwin's answer in the following April. Darwin agreed that Wallace was right in "that I came to the conclusion that selection was the principle of change from study of domesticated productions; and then, reading Malthus, I saw at once how to apply this principle. Geographical distribution and geographical relations of extinct to recent inhabitants of South America first led me to the subject: especially the case of the Galapagos Islands [41, 45]." (But the letter in which this latter statement appeared was not published until 1903.) Again Darwin expressed his admiration for the manner in which Wallace had taken the publication of the papers. Actually, it is hard to imagine what else Wallace could have done. Whatever reservations he might have had (and there is no indication that he had any), he was the forestaller, not the

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forestalled, and he had at last achieved recognition from "two of the most eminent naturalists in England," a remarkable accomplishmentfor a self-educatedcollector. Darwin had set to work again almost immediately after the publication of the papers, making an "Abstract of Species book,"and by November 1859 he could write Wallace that his publisher was sending him a copy of the Origin of Species, adding that "I do not think your share in the theory will be overlooked by the real judges, as Hooker, Lyell, Asa Gray, etc. [471."136 Darwin had hoped that Wallace would feel that his Linnean paper was "fairlynoticed"in the short Introduction and added that he would "allude"to the paper in the Annals in the body of the work [45]-this he did, but without giving either its title or the date (he always thought of this work as an abstract of the one he intended to write, and consequently he never gave proper references).1,37 But Darwin has never been accused of being overgenerousin his credits, particularly in the "HistoricalSketch"later appendedto the Originof Species, and it may be that Wallace was too modest in his claims. Wallace wrote to congratulateDarwin on his book in February 1860 [49], and Darwin sent the letter on to Lyell, remarking on "how admirably free [he was] from envy or jealousy. He must be a good fellow [53]."'This letter is among those missing, and so for Wallace's opinions it is necessary to turn to letters written to Bates in December 1860 and to his brother-in-law, Thomas Sims, in the following April. Perhaps better than anyone else, Wallace could appreciate the extraordinaryamount of work involved, and he wrote Bates that he was thankful it had not been left for him to do. "Mr. Darwin has created a new science and a new philosophy, and I believe that never has such a complete illustration of a new branch of human knowledge been due to the labours and researchesof a single man [55]." The letter to Sims is both a defense of Darwin and an explanation. Sims had apparently taken exception to Darwin's referencesto Wallace, and Wallacereprovedhim: You quite misunderstand Mr. D.'s statement in the preface and his sentiments. I have, of course, been in correspondence with him since I first sent him my little essay. His conduct has been most liberal and disinterested.I think anyone who reads the Linnean Society papers and his book will 136. Darwin had sent copies of the joint papers to Wallace the preceding year; see Appendix, 40. 137. Darwin, Origin of Species, 1st ed., pp. 1-2, 355.

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Wallace, Darwin and the Theory of Natural Selection see it. I do back him up in his whole round of conclusions and look upon him as the Newton of Natural History. Sims objected not only to the contents of the Origin of Species but even to its title. After explaining that Darwin had originally given him a different title (presumably in the letter of 13 July 1858), Wallace went on to give his own judgment of Darwin's accomplishment: "It is the vast chaos of facts, which are explicable and fall into beautiful order on the one theory, which are inexplicable and remain a chaos on the other, which I think must ultimately force Darwin's views on any and every reflecting mind." The letter is worth reading carefully because, in trying to convince Sims, Wallace showed himself a strong and articulate champion of these views [561. It is a pity that Wallace was not at home to take an active part in the controversy over the Origin of Species. He would have enjoyed the dispute which Darwin found so distasteful. But by the time he returned to England in 1862 the first heat of the battle was past. Darwin, at any rate, was pleased with Wallace's enthusiasm, and he thanked him for his "too high approbation of my book . . . most persons would in your position have felt bitter envy and jealousy [54]." 138 But the documentation of this famous episode leaves something to be desired. There are gaps in the record that not only are rarely noticed but also are being gradually obliterated in the frequent retelling of this episode. Most people agree with Marchant that Darwin's letters tell the whole story, but they form only part of the evidence. Missing are all the letters (except for one fragment) that Wallace sent to Darwin from the Malay Archipelago, Wallace's manuscript, the letters written to Darwin by Hooker and Lyell during those hectic weeks in June 1858, and the pertinent letters from Asa Gray.'39 The evidence on the disposition of the letters to Darwin is contradictory. Francis Darwin later recalled that his father "made a rule of keeping all letters that he received; this was a habit which he learnt from his father, and which he said had been of great use to him." 140 But, in describing his own work in compiling the Life and Letters of Charles Darwin, he gave a different account: 138. "Bitter envy" changed to "some envy" in Darwin, Life and Letters; see also note 150. 139. The missing letters are nos. 8, 13, 15, 20, 27, 28, 30, 38, 39, 41, 44, 48, 49, marked with an asterisk in the Appendix. Letters nos. 31 and 32 from Darwin and Hooker to Wallace are also missing. 140. Darwin, Life and Letters, I, 97.

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Of letters addressed to my father I have not made much use. It was his custom to file all letters received, and when his slender stock of files ("spits" as he called them) was exhausted, he would burn the letters of several years, in order that he might make use of the liberated "spits." This process, carried on for years, destroyed nearly all letters received before 1862. After that date he was persuaded to keep the more interesting letters, and these are preserved in an accessible form.141

Many of the letters received before 1862 do exist, however, as can easily be checked in the published collections of Darwin's letters and in the list of unpublished material in the Cambridge University Library.142 Another version of what happened to the letters is given in a biography of Hooker: In one of his letters Darwin makes special mention of preserving his friend's [i.e. Hooker's] letters. The answers to scientific questions are detached and placed among the memoranda of that subject; the other parts are put away among his general correspondence, so that it would only be a matter of half an hour to rearrange them in case of need. In spite of his care, however, a large number of the earlier letters from Hooker have disappeared wholly or in part.143 The one snippet from Wallace's letter of 27 September 1857 shows that Darwin must have followed this practice with his letters also, at least at first [16]. But Darwin was meticulous (indeed, it is from his own care in answering Wallace that the dates of Wallace's letters to him can be so easily determined). It seems surprising that all the material relating to the most dramatic (not to say traumatic) moment in his life should disappear. The dating of Darwin's own letters presents still another problem. As his son observed: He rarely dated his letters, so that but for the Diary [Journal] it would have been all but impossible to unravel the history of his books. It has also enabled me to assign dates to many letters which would otherwise have been shom of half their value,144[and] 141. Ibid., xviii-xix. 142. Cambridge University Library, Handlist of Darwin Papers at the University Library, Cambridge (Cambridge: Cambridge University Press, 1960). 143. L. Huxley, Life and Letters ... Hooker, I, 436. 144. Darwin, Life and Letters, I, xviii.

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Wallace, Darwin and the Theory of Natural Selection Mr. Darwin, who was careful in other things, generally omitted the date in familiar correspondence, and it is often only by treating a letter as a detective studies a crime that we can make sure of its date. Fortunately, however, Sir Joseph Hooker and others of Darwin's correspondents were accustomed to add the date on which the letters were received.145 Some of the crucial letters on the theory of natural selection from Darwin to Asa Gray have recently been redated by Dupree in a different connection, a redating that can be supported by an examination of the texts. These letters have appeared in different collections of Darwin's letters and have been dated 1856 [12], 1857 [14], and 1859 [17], respectively, but they seem aUl to have been written in 1857, after Darwin received Wallace's first letter. Put together and read in sequence, they seem to form a natural unit, lending support to the theory that the revelation to Gray was induced by Wallace.146 VI. EPILOGUE I feel much satisfaction in having thus aided in bringing about the publication of this celebrated book, and with the ample recognition by Darwin himself of my independent discovery of "natural selection." Wallace, Natural Selection and Tropical Nature

To a large extent the world has accepted at face value both Wallace's and Darwin's rather pious recollections of their close 145. Darwin, More Letters, I, x. 146. There are two ways to date the letters to Gray. One is by the sequence in the Darwin-Gray correspondence, and the other is from internal evidence. Both indicate that no. 12 was written in 1857. In particular, Darwin refers to a chapter on the continuous distribution of species, which "Hooker kindly read . . . over." According to Darwin's "Journal," he finished this section on 13 October 1856, having asked Hooker on 13 July 1856 if he would read it for him (Darwin, More Letters, I, 95). See also note 88. Although there is no question about the year (1857) of no. 14, Darwin did not date the copy he kept, and he thought he had sent it in October (Darwin, Life and Letters, I, 477n). The date is given as October in the letter of transmittal to the Linnean Society but as 5 September 1857 on the letter itself. See also note 90. Number 17 was probably put in 1859 because it concerns natural selection. But Darwin's book was published on 24 November, and Gray could not have received a copy, read it, and given Darwin his opinion in 5 days. Again, the sequence of letters shows that it belongs in 1857. It is followed by two others that have also been dated 1859 but which should be dated 1858, one on 21 February (Darwin, Life and Letters, I, 463-464) and another on 4 April (ibid., 510). The latter refers to a just finished chapter on instinct that, according to Darwin's "Journal," was finished on 9 March 1858. See also note 93.

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but not always unruffled relationship. The veil of Victorian propriety through which they came to view each other has, however, obscured some of their more human reactions to what must at times have been a tryingentanglement. Public recognition by Darwin of Wallace's achievement can be divided into two parts, before and after publication of the Life and Letters of Charles Darwin in 1887, the first part

consisting mainly of remarks in the "Historical Sketch" appended to the Origin of Species. This sketch (which has been called "the most unreliable account that ever will be written")'47was added to the third edition in 1861 and expanded somewhat for the fourth in 1866.148Wallace and the Linnean papers were given one sentence, while Wallace's paper in the Annals was not mentioned at all and Lyell was omitted altogether. Among the names added in 1866 were those of Patrick Matthew and William Wells, both contenders for the title of discovererof the theoryof natural selection. Matthew had written on natural selection in 1831, and he pressed his claim in the Gardners'Chronicle in 1860.149 Darwin publicly acknowledged his anticipation of the theory, writing to Wallace that "he gives most clearly but very briefly ...

our view of Natural Selection [51, 52, 54]."150 Wells' claim

was made in 1865 by a "Mr. Rowley, of the United States," for "an account of a female . . . part of whose skin resembles

that of a negro," a paper first read before the Royal Society in 1813 and published posthumously in 1818.'15 Wallace was surprised "that it should have struck no one that [his suggestion] was a great principle of universal application in Nature [60]I" Shortly before this, Wallace had modestly referred to "Mr. Darwin's celebrated theory of 'Natural Selection.' 152 Darwin had demurred,but Wallace had insisted that he would "always 147. C. D. Darlington, "The Origin of Darwinism," Sci. Amer., 200 (May 1959), 61. 148. Darwin, Origin of Species, 3rd ed., pp. v-xi; 4th ed., pp. xiii-xxi. 149. Patrick Matthew, Naval Timber and Arboriculture (Edinburgh: Longman, 1831); "Nature's Law of Selection," Gard. Chron. Agricul. Gaz., 20 (7 April 1860), pp. 312-313. 150. Darwin, Life and Letters, Jl, 95-96n. The remark on Patrick Matthew was omitted from Darwin, Life and Letters; see also note 138. 151. William Wells, Two Essays: one upon Single Vision with two Eyes; the other on Dew. A letter to . . . Lord Kenyon and an Account of a Female . . . part of whose Skin resembles that of a Negro (London: A. Constable, 1818). 152. Alfred Russel Wallace, "The Origin of Human Races and the Antiquity of Man deduced from Natural Selection," J. Anthropol. Soc. London, 2 (1864), clix.

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Wallace, Darwin and the Theory of Natural Selection maintain it to be actually yours, and yours only [57, 58]." And yet in 1869 Wallace's reply to a request from the anthropologist A. B. Meyer for his recollections of his part in the theory was brusque. After stating that he "was led to it by Malthus' views on population applied to animals," his terse account ended with the remark that his paper "was printed without my knowledge, and of course without any correction of proofs. I should, of course, like this fact to be stated [63]." Wallace objected to being classed with Matthew and Wells, "who made no further use of that principle, and failed to see its wide and immensely important applications," and he published a collection of his papers in 1870 to make the extent of his own contribution clear.153 But he did not then, nor did he ever, claim that he had worked out the theory in the detail that Darwin had. Darwin thanked Wallace in glowing terms for the kind words in his preface, having missed altogether the point about Matthew and Wells [65]. Lyell, in the meantime, thought Darwin had given short shrift not only to Wallace and himself, but also to Lamarck. He was astonished to find no mention of Wallace's paper in the Annals in Darwin's "Historical Sketch" [61], and he discussed this "next important effort to determine the manner in which new species may have originated" in some detail in the new edition of his famous Principles of Geology, published in 1867-1868.154 He had already credited Wallace with thinking out, "independently for himself, one of the most novel and important of Mr. Darwin's theories," in discussing the joint papers in his Antiquity of Man.155 And in his Principles of Geology, he now reprinted in its entirety his original summary of Lamarck, not to protest against his theory of the transmutation of species as before, but to "show how nearly the opinions taught by him at the commencement of this century resembled those now in vogue." 156 As for himself, Lyell wrote in a letter to Ernst Haeckel in November 1868 that he was obliged to him "for pointing out [in his History of Creation] how clearly I advocated a law of continuity even in the organic world, so far as possible without adopting Lamarck's theory of transmutation . . . I had certainly prepared the way in this country . . . for the reception of Darwin's gradual and insensible evolution of species [62]," and Huxley later agreed with him.157 In 1870, apparently in 153. 154. 155. 156. 157.

Wallace, Contributions, p. iv. Lyell, Principles of Geology, 10th ed., II, 276-281. Lyell, Geological Evidences, 1st ed., pp. 408-409. Lyell, Principles of Geology, 10th ed., II, 246n. Darwin, Life and Letters, I, 543-544.

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reference to the preface to Wallace's compilation of his papers, Lyell again supported Wallace, writing him that "it is high time this modest assertion of your claims as an independent originator of Natural Selection should be published [64]." Not until the publication of the Life and Letters of Charles Darwin in 1887, five years after Darwin's death, did Wallace receive full public recognition for his part in the theory of natural selection. The letters from Darwin to Hooker, Lyell, and Wallace himself were there for all to read (although neither the complete texts nor all of the early letters from Darwin to Wallace were included 158); and as further proof of Wallace's role in inducing Darwin to publish the Origin of Species, there was also Darwin's "Autobiography." For the first time, Wallace learned some of the details of those long-ago events. He was surprised to find that Darwin "had been so distressedor rather disturbed" by his essay, and he wrote apologetically to Francis Darwin that he had always felt that he had received too much credit "for my mere sketch of a theory [68]." Darwin's attitude had also softened. Nearly twenty years after the event, in an autobiographical sketch written mainly for the eyes of his children, he could say that he "cared very little whether men attributed most originality to me or Wallace." 159 He had worried whether Wallace would consider the whole proceeding justifiable (about which both he and Hooker seemed to have some lingering doubts), not then knowing "how generous and noble was his disposition." 100 He mentioned once again that his own parts of the joint papers had not been intended for publication, while Wallace's was a model of clarity. He never recognized in any way that Wallace's was hastily written, that it had not been intended for publication either, or that Wallace had had no chance to proofread it, but he did credit Wallace with giving him the impetus that produced the Origin of Species. Now that Wallace's position was secure, he began to embroider his own recollections. At the time he wrote his essay, nearly thirty years before, he had had no idea either of its importance or of its impact on Darwin, and the earliest re158. Of the first eight extant letters from Darwin to Wallace, six are included in Darwin, Life and Letters (nos. 11, 18, 43, 46, 47, and 54), but only one (47) is complete. The seventh (45) is in Darwin, More Letters, and the eighth (50) is in Marchant, Wallace. Marchant includes the complete extant text of all of them, but his book was not published until 1916. The texts also differ slightly from those in Darwin, Life and Letters. See also notes 3, 87, 135, 138-143, 146, 150, and 171. 159. Darwin, Life and Letters, I, 71. 160. Ibid., 69.

314

Wallace, Darwin and the Theory of Natural Selection quest for his memories had come from Meyer in 1869. But now the circumstances of that week so long ago assumed a new interest. Alfred Newton, ornithologist and zoologist, wrote inquiring for details to incorporate in his review of the Life and Letters of Charles Darwin, and Wallace obligingly responded. But the letter to Newton [69], written in 1887, contains a number of questionable statements. Wallace was now uncertain whether he had even read Darwin's Voyage of the Beagle at the time, when he had in fact read both editions and had the second one with him in the Malay Archipelago; scattered references to Darwin in his own early published works also show that he had read him with some care. He thought he had started the correspondence over some peculiar varieties of ducks. However, the letter itself shows that he was consulting the Life and Letters of Charles Darwin to refresh his memory, and the paragraph containing the request for "any curious breed" in Darwin's first letter to him was omitted there. Evidence from Wallace's "Notebook" also indicates that Darwin brought the subject up first [11].161 Notices in the Athenaeum that Darwin was interested in species and varieties seem improbable.162 Wallace again paid his respects to Malthus, further enshrining him in the annals of science. And finally, he referred to a "hot fit" of intermittent fever, although he later said the idea had come to him during a "cold fit." Wallace had returned only a few months before from a speaking tour of the United States. Interestingly enough, he had met Asa Gray during a month-long stay in Boston, and Gray had invited him to attend a meeting of the Cambridge Scientific Club. There, Gray showed his correspondence with Darwin before the publication of the Origin of Species, 161. See also notes 86 and 87. 162. No such notices located. Although it is possible that Wallace heard of Darwin's interest through his agent, Stevens (who had been a member with Darwin since 1837 of the Entomological Society), and he could have used them as an opening for his first letter in 1856 (8), this still would not account for the range of subjects he apparently discussed. Darwin answered: "By your letter and even still more by your paper in the Annals . . . ," indicating that the letter itself must have contained some related remarks (11). Sydney Smith has suggested (personal communication) that two letters from Darwin to W. B. Tegetmeier, dated 21 Nov. and 29 Nov. 1857, show that it was about the second date that Darwin received some poultry specimens collected by Wallace. Since Wallace received Darwin's letter (11) with this request in July (see 19), the shipment could have been in response to that request. This would leave unaffected the first letter Wallace wrote to Darwin in October 1856 (8), and the reason for it would then remain an open question.

315

BARBARA G. BEDDALL

and Wallace "related what led him to his theory of Natural Selection . . . The writings of Spencer, Vestiges of Creation,

Lamarck?,but particularlyof Malthus on population suggested his own view."163 This also seems inaccurate: Wallace omitted Lyell and added Spencer, whose First Principles he read after his return from the Malay Archipelago, in September 1862.1'4

At any rate, perhaps heartened by the public recognition he had now received, Wallace expanded his series of lectures into a book, published in 1889, to which he gave the title, Darwinism: An Exposition of the Theory of Natural Selection.

To him the terms were synonymous. Furthermore,he was still convinced of the prime importance of natural selection, although Darwin had staged a gradual retreat from this position. Next, in the introductorynote to a chapter in a new compilation of his papers, Natural Selection and Tropical Nature, Wallace added further details of that now never-to-be-forgotten week, even to the temperatureoutside. Again he consulted the Life and Letters of Charles Darwin, and another probableerror crept into the story. From the dates on which the first two Darwin letters were written, Wallace presumed that he had received them before sending his paper to Darwin, and he quoted from them both. It is unlikely, however, that the second letter could have reached him so quickly. But he was now satisfied, as can be seen from his concluding remark, "with the ample recognition by Darwin himself."165 Wallace gave an even more detailed account in his own autobiography,written nearly fifty years after the event, adding, among other things, that he had asked Darwin to show his paper to Lyell "who had thought so highly of my former paper." This again presumes that Wallace had already received Darwin's second letter, which is doubtful. This frequently quoted-fromaccount should be treated with caution.'66 In thanking Wallace for a copy of his Life, Hooker, now eighty-eight years old, remarked that "yourcitation of my letters and their contents are like dreams to me; but to tell you the truth, I am getting dull of memory as well as of hearing, and what is worse, in reading: what goes in at one eye goes out at the other"-perhaps an honest evaluation that could be applied to most octogenarians, including Wallace.'67 163. Cambridge Scientific Club, "Record Book," 17 November 1886, MS, Harvard University Archives; quoted with the perrmission of Harvard University. See also Dupree, Asa Gray, pp. 380, 473 n52. 164. Marchant, Wallace, p. 122. 165. Wallace, Natural Selection, pp. 20-21. 166. Wallace, My Life, I, 357-363. 167. Marchant, Wallace, p. 332.

316

Wallace, Darwin and the Theoryof Natural Selection On 1 July 1908, the Linnean Society held a jubilee to commemorate the reading of the joint papers fifty years before. It seems extraordinarythat two of the protagonists, Wallace and Hooker,were still alive and able to participate. (Lyell had died in 1875 and Darwin in 1882.) Wallace, the first of the two to speak, repeated his story with some new elaborations, helping to perpetuate the (perhaps fictitious) report that his paper had come to Darwin 'like a thunderbolt from a cloudless sky," but his account was modest and self-effacing.'68 He was, after all, a modest man. He had refused some of the honors offeredhim and had accepted others (such as an honorary degree from Oxford and a Fellowship in the Royal Society) only after strong urging. He had long since received the credit he felt due him as an independent originator of the theory of natural selection. In the published report of the proceedings, Wallace added some selections from the sixth edition of Malthus that he thought might have influenced him, remarking, however, that it was the over-all effect rather than particular details that he remembered. He concluded with a well-deserved tribute to Lyell who had, as he said, impressed him even more deeply than Malthus.'69 Then it was Hooker's turn. It is startling to discover that Hooker'sfirst biographer,Leonard Huxley, referred to Hooker as the "sole survivor of those immediately concerned,"dismissing Wallace altogether (an oversight repeated by his latest biographer),170and he mentioned just as casually that "one or two of the letters that then passed were missing."171 But Hooker, in accepting the invitation to speak, was rather anxious not only about the expediency and propriety of telling the public what he had done, but also about the accuracy of his recollections. He appealed to Sir Francis Darwin and to Sir Leonard Lyell, Sir Charles'snephew, for help in finding additionaldocumentary evidence. But none could be found, and he was forced to rely entirely on the partial story in the Life and Letters of CharlesDarwin. He carefully noted this in his speech, apologizing at the end for "thehalf-century-oldreal or fancied memories of a nonagenarian."172 But Wallace had saved the early letters he received from 168. Linnean Society of London, The Darwin-Wallace Celebration, pp. 5-11. 169. Ibid., pp. 111-118. 170. Mea Allan, The Hookers of Kew, 1785-1911 (London: Michael Joseph, 1967), p. 248. 171. L. Huxley, Life and Letters . .. Hooker, II, 465. 172. Linnean Society of London, The Darwin-Wallace Celebration, pp. 11-16.

317

BARBARA G. BEDDALL

Darwin (except for one), althoughthe manuscriptof his famous paper was never found. On the outside of an envelope in which he kept the letters, Wallace wrote: The first 8 letters I received from Darwin-while in the MalayArchipelago. NB. The MSS. of my Paper sent to Darwin and printed in the Journal of the Linnean Society, was not returned to me, and seems to be lost. The proofs with the MSS. were perhaps sent to Sir Charles Lyell, or to the Secretary of the Linn. Soc. & may some day be found. It was written on thin foreign note paper.'73 However, "neither Wallace's part of this correspondence,nor the original MS. of his essay . . . has been discovered," as

Marchantwrote after Wallace'sdeath.'74 And so the story rests, with some questions still unanswered. Why did Wallace first write to Darwin? Why did Darwin send the outline of his theory of natural selection to Asa Gray? What became of the letters Darwin received from Wallace, Lyell, Hooker, and Gray? Where is Wallace's manuscript? The answers are in the missing material, and what really happened must remain speculation. The fact that much other material is also missing does not invalidate the point that evidence to supportsome commonly accepted explanations is inadequate or lacking and that other explanations are clearly in error. ACKNOWLEDGMENTS I would like to express my appreciation to Dr. Ernst Mayr for critically reading the manuscript, and to Dr. Everett Mendelsohn for editorial help in preparing it for publication. I would also like to thank Miss Sandra Raphael, Librarian of the Linnean Society of London, for her kind assistance. Finally, I would like to acknowledge my husband's encouragement and financial support,without which this would not have been done. 173. Marchant, Wallace, p. 106. 174. Ibid., p. 105.

318

APPENDIX * LETTERS

No.1

From - to

Sources3

Date2

Comments

1.

A. R. WallaceH. W. Bates

11 April 1846

W, 1, 255-256; M, 21.

Omission in M.

2.

A. R. WallaceH. W. Bates

9 Nov. [1847]

W, 1, 254; M, 73.

For dating, see note 14.

3.

A. R. WallaceH. W. Bates

28 Dec. [18471

W, 1, 254-255; M, 73-74.

Omission in M; for dating, see note 14.

4.

A. R. WallaceH. W. Bates

[Early 1848]

W, 1, 256-257; M, 74-75.

Omission in M.

5.

C. DarwinC. Lyell

3 May [1856]

DLL, 1, 426-427; DLLE, 2, 67-68.

6.

C. Darwin3. D. Hooker

9 May [1856]

DLL, 1, 427-428; DLLE, 2, 68-69.

7.

C. DarwinJ. D. Hooker

11 May [1856]

DLL, 1,428-430; DLLE, 2, 69-71.

*8.

A. R. WallaceC. Darwin

[10 Oct. 1856]

H. W. BatesA. R. Wallace

19 Nov. 1856

M, 52-53.

10.

C. DarwinW. D. Fox

22 Feb. 1857

DLL, 1, 452; DLLE, 2, 94-95.

11.

C. DarwinA. R. Wallace

1 May 1857

DLL, 1, 452-454; DLLE, 2, 95-96; M, 107-109.

Answer to 8, received July 1857; see 19. Omissions in DLL; see notes 86, 87, and 162.

12.

C. DarwinA. Gray

20 July [1857]

DLL, 1, 437-438; DLLE, 2, 78-80; Du, 244-245,458 n22.

See also 14 and 17. For dating, see note 146.

*13.

A. GrayC. Darwin

[Aug. 1857]

-

See 14.

9.

Received late April 1857; see 11 and 69, and notes 43, 81, and 162. Received July 1857; see 19.

319

Letters (continued) No.1

From - to

14.

C. DarwinA. Gray

5 Sept. [1857]

A. GrayC. Darwin

[Autumn 1857]

16.

A. R. WallaceC. Darwin

[27 Sept. 1857]

CUL

Unpublished fragment of answer to 11. Received Dec. 1857; see 18. See also notes 60, 95, 142, and 143.

17.

C. DarwinA. Gray

29 Nov [1857]

DML, 1, 126-127; Du, 247,459 n24.

Not published undl 1903. See also 12 and 14. For dating, see note 146.

18.

C. DarwinA. R. Wallace

22 Dec. 1857

DLL, 1,465-467; DLLE, 2, 108-110; M, 109-111.

Answer to 16. Omission in DLL.

19.

A. R. WallaceH. W. Bates

4 & 25 Jan. 1858

W, 1, 358-359; M, 53-55.

Answer to 9. Omissions in W, and texts differ slightly; here quoted from M. See also note 94.

*20.

A. R. WallaceC. Darwin

[Feb. 1858]

21.

C. DarwinJ. D. Hooker

8 June [1858]

DML, 1, 109.

22.

C. DarwinC. Lyell

18 June [1858]

DLL, 1, 473; DLLE, 2, 116-117.

23.

C. DarwinC. Lyell

[25 June 1858]

DLL, 1, 474-475; DLLE, 2, 117-118.

24.

C. DarwinC. Lyell

26 [June 1858]

DLL, 1, 475; DLLE, 2, 118-119.

25.

C. DarwinJ. D. Hooker

[29 June 1858]

DLL, 1, 476; DLLE, 2,119.

26.

C. DarwinJ. D. Hooker

[29 June 1858]

DLL, 1, 476-477; DLLE, 2, 119-120.

*27.

C. LyellC. Darwin

[June 1858]

See 25 and notes 3, 139-143, and 171.

*28.

J. D. HookerC. Darwin

[June 1858]

See 25 and 26, and notes 3, 139-143, and 171.

*15.

320

Date2

Sources8 JLZ, 3, 50-53; DLL, 1, 477-482; DLLE, 2, 122-125; Du, 246,458-459 n23.

Comments See also 12 and 17. Many differences in texts between JLZ and DLL. For dating, see note 146; see also note 92. See 17.

Received 18 June 1858; see 22. See also note 116. Not published until 1903.

Letters (continued) No.1

From - to

Sources8

Date2

Comments

29.

C. DarwinJ. D. Hooker

S July [1858]

*30.

J. D. HookerC. Darwin

[July 1858]

*31.

J. D. HookerA. R. Wallace

[13? July 1858]

Received early October 1858; see 33, 37, and 42.

*32.

C. DarwinA. R. Wallace

[13 July 1858]

Answer to 20, received early October 1858; see 33,37, and 42.

33.

C. DarwinJ. D. Hooker

[13 July 1858]

DLL, 1,484-485; DLLE, 2, 128-129.

34.

C. DarwinC. Lyell

18 July [1858]

DLL, 1,485-486; DLLE, 2,129-130.

35.

C. DarwinJ. D. Hooker

21 July [1858]

DLL, 1, 486-487; DLLE, 2, 130-131.

36.

C. DarwinJ. D. Hooker

[5 Aug. 1858J

DLL, 1,489-490; DLLE, 2,133.

37.

A. R. Wallacehis mother

6 Oct. 1858

W, 1,365; M, 57-58.

*38.

A. R. WallaceC. Darwin

[Oct. 1858]

Received [22] January 1859; see 43.

*39.

A. R. WallaceJ. D. Hooker

[Oct. 1858]

Received [22] January 1859; see 43.

40.

C. DarwinJ. D. Hooker

12 Oct. 1858

*41.

A. R. WallaceC. Darwin

[30 Nov. 1858]

42.

A. R. WallaceG. Silk

[Nov. 1858]

W, 1,365-367.

43.

C. DarwinA. R. Wallace

25 Jan. [1859]

DLL, 1, 501-502; DLLE, 2, 145-147; M, 111-112.

*44.

A. R. WallaceC. Darwin

?

45.

C. DarwinA. R. Wallace

6 April 1859

DML, 1, 118-120; M, 112-114.

Answer to 41, but not published until 1903.

46.

C. DarwinA. R. Wallace

9 Aug. 1859

DLL, 1, 516-517; DLLE, 2, 161-162; M, 114-115.

Answer to 44; omission in DLL.

47.

C. DarwinA. R. Wallace

13 Nov. 1859

DLL, 2, 16-17; DLLE, 2, 220-221; M, 115-116.

DLL, 1, 482-484; DLLE, 2,124-127. -

See 33.

Omissions in W.

DLL, 1,494; DLLE, 2, 138. Received 6 April 1859; see 45.

Answer to 38; omissions in DLL. Received 7 August 1859; see 46.

321

Letters (continued) No.1

From - to

*48.

A. R. WallaceC. Darwin

?

Received March? 1860; see 50.

*49.

A. R. WallaceC. Darwin

[16 Feb. 1860]

Received 18 May 1860; see 54.

50. C. Darwin-

Date2

7 March 1860

Sources3

M, 116.

A. R. Wallace

Comments

Answer to 48; not published until 1916.

51.

C. DarwinC. Lyell

10 April [1860]

DLL, 2, 93-95; DLLE, 2, 300-301.

52.

C. DarwinJ. D. Hooker

[13 April 1860]

DLL, 2, 95-96; DLLE, 2,301-303.

53.

C. DarwinC. Lyell

18 May [1860]

DLL, 2, 101-102; DLLE, 2, 308-309.

54.

C. DarwinA. R. Wallace

18 May 1860

DLL, 2, 102-103; DLLE, 2,309-310; M, 117-118.

Answer to 49. Omissions and changes in DLL; see notes 138, 150.

55.

A. R. WallaceH. W. Bates

24 Dec. 1860

W, 1,373-375; M,59.

Omissions in M.

56.

A. R. WallaceT. Sims

15 March 1861

M, 59-67.

57.

C. DarwinA. R. Wallace

28 [May? 1864]

DLL, 2,271-273; DLLE, 3,89-91; DML, 2,32-34; M, 127-128.

58.

A. R. WallaceC. Darwin

29 May [1864]

DML, 2,34-37; M, 128-131.

59.

C. DarwinJ. D. Hooker

[Oct. 1865]

DLL, 2, 225; DLLE, 3, 41.

60.

A. R. WallaceC. Darwin

19 Nov. 1866

M, 145-146.

61.

C. LyellA. R. Wallace

4 April 1867

M, 279-281.

62.

C. LyellE. Haeckel

23 Nov. 1868

LLL, 2,435-437.

63.

A.R. WallaceA. B. Meyer

22 Nov. 1869

Nat., 52 (1895), 415. Not published in its entirety until 1895.

64.

C. LyellA. R. Wallace

15 Feb. [1870?]

M, 288-289.

65.

C. DarwinA. R. Walace

20 April [1870]

DLL, 2, 301-302; DLLE, 3,121; M, 206-207.

66.

G. BenthamF. Darwin

30 May 1882

DLL, 2, 87-88; DLLE, 2,293-294.

322

Letters (continued) No.1

From - to

Date2

Sources8

67.

J. D. HookerF. Darwin

22 Oct. 1886

HLL, 2, 300-302.

68.

A. R. WallaceF. Darwin

20 Nov. 1887

M, 295.

69.

A. R. WallaceA. Newton

3 Dec. 1887

DAU, 200-201; DAUE, 189-190.

Comments

See also notes 7, 39-41,43,81,86, 87, 161, and 162.

1. Missing letters, known to have existed from other correspondence, are marked with an asterisk; see "Comments". 2. Uncertain dates of special interest here are discussed in the notes; see "Comments". 3. Sources are arranged chronologically. Most of them are fully cited in the notes, the rest here. They are abbreviated as follows: CUL Cambridge University Library. DAU Francis Darwin, ed., Charles Darwin: His Life Told in an Autobiographical Chapter and in a Selected Series of His Published Letters (New York: D. Appleton, 1892). DAUE English edition of above (London: Murray, 1892). DLL F. Darwin, Life and Letters of Charles Darwin. DLLE English 3-volume edition of above (London: Murray, 1888). DML F. Darwin, More Letters of Charles Darwin. Du Dupree, Asa Gray. HLL L. Huxley, Life and Letters of Sir Joseph Dalton Hooker. JLZ Journal of the Linnean Society of London (Zoology). LLL K. Lyell, Life, Letters and Journals of Sir Charles Lyell. M Marchant, Alfred Russel Wallace. Nat. Nature. W Wallace, My Life.

323

Notes on SourceMaterials: The Edwin GrantConklinPapersat PrincetonUniversity GARLAND E. ALLEN Department of Biology, Washington University, St. Louis, Missouri DENNIS M. McCULLOUGH Harvard Medical School

The period between 1890 and 1930 was one of momentous transition in the history of modern biology. These years saw the introduction of experimental and quantitative techniques into areas of biology which had traditionally been desc iptive and qualitative. In particular, the fields of embryology, heredity, and organic evolution, were all revolutionized by the advent of experimental and mathematical analysis. Long-standing problems such as the mechanisms of embryonic differentiation and of hereditary transmission, or of the origin of species, were approached through new conceptual schemes and seemed, in some quarters at least, to have been solved at last. Yet the introduction of these techniques was not accomplished overnight, or received with universal acclaim. The transformation of biology as a whole from the morphological tradition of the nineteenth century to the experimental tradition of the twentieth was accompanied by much debate about what constituted a meaningful explanation in the life sciences. In evaluating this important period of transition the historian must look behind the public statements of research workers and seek out the origins of attitudes of individuals and of groups. In short, he must try as best he can to understand both how and why certain changes in thought patterns came about within the community of working biologists at the time. One of the historian's most valuable sources in this regard is the use of manuscript materials, in which a man's more candid opinions are often expressed, his indebtedness to others often undisguised, and the interplay of personalities can be

325

GARLAND E. ALLEN

DENNIS MCCULLOUGH

seen in its most vivid light. Especially useful to the historian of this period of biological history is the large collection of personal papers of Edwin Grant Conklin (1863-1952), one of America's foremost biologists during the period 1900-1945. The papers include letters containing valuable information about current ideas, books, organizations, journals, and per-

sonalities in the scientific world. In addition, the collection contains manuscripts of lectures, outlines of courses, reading notes, and rough drafts of books or articles-primarily for the period 1890-1945.1 As a student of William Keith Brooks at Johns Hopkins Universityin the 1880's, Conklinwas among the first generation of Americanbiologists to take most if not all of their advanced training in this country. As a scholar and teacher, Conklin came into contact with some of the finest scientific minds of the times. His correspondents, for example, included J. McKeen Cattell, C. B. Davenport, Harold Heath, H. S. Jennings, G. H. Parker,RaymondPearl, Ross G. Harrison, T. H. Morgan, E. B. Wilson, Fritz Baltzer, C. B. Bridges, Hugo de Vries, Reinhardt Dohrn (son of Anton Dohrn), Hans Driesch, Richard Goldschmidt,Henry FairfieldOsborn,W. J. V. Osterhout,Oscar Riddle,Hans Spemann, and W. M. Wheeler. Trained as an embryologist, Conklin's interest in this and related fields extended over a period of nearly fifty years. Of interest to the historian of embryology are not only the personal letters between Conklin and embryologistssuch as T. H. Morgan,Hans Driesch, and Hans Spemann,but also such items as the manuscript of a lecture delivered at the Marine Biological Laboratoryat Woods Hole, Massachusetts,in 1941. In this lecture Conklin traced the developmentof embryologicaltheory from the descriptivestudies of Balfour, T. H. Huxley and W. K. Brooks in the nineteenth century to the experimental work of Roux, Driesch, and Spemann in the twentieth. In evaluating the influences which came to bear on his own thinking about the problems of development, Conklin had a somewhat different view from his close friend, T. H. Morgan. To Conklin, descriptive studies and the detailed, careful analyses of cell linkage to which he himself had devoted considerable effort, 1. Several collections of this sort, of interest to the historian of twentiethcentury biology, are in existence, among them the Jacques Loeb papers, Library of Congress, Washington, D.C.; the Ross G. Harrison papers, Yale University; the C. B. Davenport papers, American Philosophical Society; and the Richard Goldschmidt papers, University of California at Berkeley. Only one such collection, however, has been described in print: "Jacques Loeb the Scientist, His Papers and His Era," by Nathan Reingold in Lib. Cong. Quart. J. Recent Acquisitions (1962), pp. 119-130.

326

Notes on Source Materials were important parts of embryological study. To Morgan, however, the older morphological studies were distinctly secondary to the more recent experimental analyses. Thus Conklin attributed somewhat less influence to the work of experimentalists like Driesch and Roux, and more to men like Brooks and Weismann. To Conklin, the new experimental embryology constituted less of a break with the past than to Morgan. Yet to both men, as to most embryologists, the essential problem was, how does cellular differentiation occur? Letters between Conklin, Morgan, E. B. Wilson and others indicate the kinds of approaches taken at this time to embryological problems, and how these approaches were influenced by new techniques and methods of analysis. Because of a long-standing interest in organic evolution, Conklin wrote and spoke much on this subject from the mid 1890's until the 1940's. In the early years (1890's to 1915) Conklin, like many biologists at this period, was skeptical of natural selection as the only mechanism by which evolutionary change could occur. Influenced as he was by de Vries' mutation theory, he tended to think of evolutionary development in terms of discrete changes rather than continuous, almost imperceptible, variation from one generation to another. Between 1915 and 1920, however, he became an outspoken advocate of natural selection coupled with small mutations as the all-sufficient mechanism for evolutionary change. His views on evolution brought Conklin into the flurry surrounding the Scopes trial in 1925. Asked to attend the trial by Forest Bailey, associate director of the American Civil Liberties Union, Conklin sought advice from personal friends as well as professional colleagues about what could and should be done to help the cause of scientific and educational freedom. Although his health finally prevented him from taking an active part in the trial itself, Conklin exchanged letters with many of the important scientists who attended the Dayton trial either as observers or witnesses. The reaction of Conklin and his colleagues to such personalities as Clarence Darrow and William Jennings Bryan is of value to the historian interested in social, political, or intellectual history. Through his studies in embryology and evolution, Conklin was led to the perennial problem of heredity. A series of lectures which he delivered at Northwestern University in 1894 and 1895 provide a good summary of knowledge and speculation on this subject in the pre-Mendelian era. Since Conklin himself was committed to no single system, such as that of the neo-Lamarckians or of Weismann, his lectures represent

327

GARLAND E. ALLEN

DENNS MCCULLOUGH

an attempt to evaluate various schemes objectively. Later, in a large number of lectures on heredity delivered during the period 1900 to 1910, as well as in some of his correspondence (as, for example, with Raymond Pearl) Conklin expressed a strong skepticism toward Mendelian heredity. At the time he felt the facts did not warrant the extension of Mendelian principles to all types of organisms, and as an embryologist he felt, like Morgan, that particulate theories of inheritance smackedof the old doctrineof preformation. One of the questions of prime importance to biologists in the late 1890's and early 1900's was that of sex determination. In the nineteenth century, opinion on this subject was divided between those who felt that sex was genetically determined at the moment of fertilization and those who felt that it was deter-

mined during developmentby some external addition (such as temperature, amount of nourishment, pH, and so on). It was shortly after 1900 that attention began to focus on the chromosomes, and particularly on the unpaired or unequally paired chromosomes, as possible mechanisms for understanding the inheritance of sex. Biologists, however, seldom agreed upon observed numbers, identities, sizes, and behavior of these chromatin-or chromatin-like--bodies (the accusation that a nucleolus was being mistaken for a chromosome was hurled at least once). An interesting exchange of letters between Conklin and Miss Katharine Foot, a cytologist working on this problem, provides an extensive and informative picture of the kind of questions and problems which were facing those who attempted to relate studies in heredity to those in cytology. In 1906 and 1907 Miss Foot was engaged in a controversywith E. B. Wilson over the chromosome interpretation of sex inheritance. Conklin was evidently her scientific mentor, and one letter which she wrote in 1907 is a good example of the kind of informationavailableto the scholarin this collection. Dear Conklin, It was awfully nice of you to write us that letter. We really thought you were disappointed in the paper as well as the photos and as we thought we had set up a pretty good case for our side of the fight, we were naturally disappointed. Some of your corrections we had already made in our copy and we have acted on all your suggestions-making also those points clearer that were so muddy you misunderstood them. We expect Wilson to give us the Devil of course, but as long as we stick to our facts and do not exaggerate

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Notes on Source Materials them, we need not be afraid of him. We have decided to stick to Anasa this Summer and work on the problem of individual variation in the chromosomes-not so much variation in different individuals but variation in the same individual. E. B. is evidently going to crawl through the hole of individual variation. In his last paper he finds one individual with 25 sp-gonial chromosomes instead of 22 or 23 as his theory demands. It seems to us it ought to be shown whether variations in the size, form, grouping, etc. of the chromosomes are found in different individuals only, (as E. B. certainly insinuates) or whether an equal amount of variation can be found in the same individual. Isn't E. B. a curiosity? Do you note that his s-chromosome (in his last paper) is much smaller than a centrosome and yet it never seems to occur to him that it might elude his eagle eye. He prefers to explain inconsistencies by an elaborate theory. We are going to work a little on Lygarus-just to have a peep at those Idio-chromosomes for our own satisfaction, but even if we find things to our satisfaction, we think it would look too personal to attack E. B. again quite so soon. Of course if he goes for us too hard, we may feel differently. Don't you think we are right to go a little deeper into Anasa now that we have our methods in shape to do it satisfactorily? We both send much love to Mrs. Conklin and again thanks to you for all your valuable suggestions and corrections. Sincerely yours, KATHERINE

FOOT

The Foot correspondence alone is worth careful study, rewarding not only because of its contents, but also because of the delightfully humorous vein in which it is written. Similarly, correspondence with men such as Harrison, Wilson, and Morgan provides insight into the rationale and philosophy behind the founding of the Journal of Experimental Zoology ( 1904). An exchange of letters, particularly between Conklin and Harrison, details the thinking that led to the recognition of both the need for and the subsequent influence of a journal which would provide an organ for the publication of experimental, rather than morphological or descriptive papers. A detailed study of the founding of this journal might be of considerable help in documenting the growth of experimentalism in American biology.

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GARLAND E. ALLEN

DENNIS MCCULLOUGH

Conklin himself was aware of living in a transition period in biological history. A definite advocate of experimental as opposed to purely observational and descriptive methods, he was not, however, a leader in turning men's minds away from the old. He had a personal fascination for speculation and philosophywhich he no doubt inherited from his teacher W. K. Brooks. At Princeton in the 1920's and thirties Conklin gave a course on "philosophicalbiology,"the outline and reading list for which are contained in the collection. At one place on his outline he penciled "Fact never as interesting as fancy," a brief but revealing indication of his own predilections. Yet he did believe that biology could only progress as a science by the introduction of careful observation, experimental analysis, and the methods of physics and chemistry. His exchange of letters with T. H. Morgan, a strong advocate of experimentalism, gives an indication of the explicitness with which workers in that period considered the problems of method in biology. This particular correspondence describes in nice detail how the new methodology (that is, experimental analysis) was first introduced into classically descriptive areas through embryology. One of the items missing from the Conklin collection is the folder of correspondencefrom his old teacher at Johns Hopkins, W. K. Brooks, an enigmatic figure in the history of American biology. Although his own scientffic work was almost purely of a descriptivenature, he was nevertheless the teacher of four of the greatest experimentalbiologists of the twentieth century: E. G. Conklin,R. G. Harrison,E. B. Wilson, and T. H. Morgan.It has been generally assumed in the past that Brooks was an enormously influential teacher whose methods of instruction as well as research turned out exceptional students. Yet, interestingly enough, none of Brooks' best students ever followed up the kind of work which he himself pursued as investigator and few have recorded explicitly any sense of intellectual debt to him. Conklin was the closest of the group to Brooks, however, and it is more than likely that in their correspondence some sense of Brooks's influence might become apparent.This materialis currentlybeing traced. A number of specific and interesting research projects could grow out of information in the Conklin collection. One would be a detailed study of Conklin's changing views on such matters as Mendelian heredity or Darwinian selection during the period 1890-1910/15. This seems to parallel, in its broadest outlines, a similar change in view on the part of T. H. Morgan. Such a study would tend to indicate to what extent the change 330

Notes on Source Materials was for particular personal reasons, and to what extent it reflected increase in available data and methods common to the biological community as a whole. Another topic would be a study of Conklin's changing views on biological methodology, from his student days at Johns Hopkins until 1920 or 1930. This should provide a valuable case study of the introduction of experimental methods into classical areas of biology. Still a third project might well center around Conklin's role in founding the Journal of Experimental Zoology in 1904. Although Ross Harrison was the primary organizing force in this endeavor, Conklin and others were enormously influential in shaping editorial policy and in reviewing individual papers. Valuable information for the intellectual historian lies in correspondence which discusses papers contributed to the Journal. The reasons why papers were accepted or rejected provide useful insights into what was considered (at least by the editorial board) valuable method and subject for biological research. In summary, the Conklin papers provide a revealing and intimate view of an era in biological history. It was an era of change and excitement-one ripe for study especially by the scholar interested in the history of evolutionary and embryological theory. Coming out through the many letters and notes are the captivating personalities of such workers as Conklin, Morgan, Wilson, H. F. Osborn, and Katherine Foot. Not only does such information add life to what otherwise becomes paper-thin history, but it also forms important source material for biographical studies. The Conklin papers thus provide an important handle-one seldom found in published research papers-for coming to grips with the intellectual and psychological climate of opinion among biologists in the early years of this century.

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In addition to essay reviews, the Journal will carry brief descriptive notes of selected books which have been received for review and of new journals or other periodicals related to the history of the biological sciences. A Naturalist in Russia; Letters from Peter Simon Pallas to Thomas Pennant. Ed. C. Urness. University of Minnesota Press, 1967; 189 pp.; $7.50. Pallas, an eighteenth-century German naturalist, worked and traveled extensively in Russia and Siberia under the patronage of Catherine II. His letters to Pennant, an English colleague, combined with Urness' detailed footnotes, provide an often illuminating account of science and of life in Russia in the eighteenth century. Agassiz, Louis. Bibliographia zoologiae et geologiae. (London: The Ray Society, 1848-1854) New York: Johnson Reprint Corp., 1968; 4 vols.: 529, 495, 661, 707 pp.; $150.00. An alphabetically arranged author catalogue of books, tracts, and memoirs on zoology and geology which provides a basic bibliographic source for biology before 1850. Ancient Medicine. Selected Papers of Ludwig Edelstein. Ed. Owsei Temkin and C. Lillian Temkin. Baltimore: The Johns Hopkins Press, 1967; xiv + 496 pp.; $12.50. The four parts of this handsome volume bring together the bulk of Edelstein's contributions to the history of ancient medicine in over thirty years of scholarly research. Part 1 deals with Greek medicine from Hippocrates to the Methodists; pt. 2 considers the influence of empiricism and skepticism, the relation of medicine to religion and magic, and the practice of anatomy and dietetics in Greek and Roman medicine; pt. 3 examines the relations of medicine to the professional ethics of the Greek physician and to the Greek philosophy and ethos; essays in pt. 4 treat more general medico-historical themes. Baltzer, Fritz. Theodor Boveri. The Life and Work of a Great

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Biologist. Trans. Dorothea Rudnick. Berkeley: University of California Press, 1967; xviii + 165 pp., illus.; $5.50. Professor Baltzer, a student and colleague of Boveri's, first chronicles Boveri's life and personality and then explores his scientific work within its historical setting. He describes many of Boveri's pivotal experiments in embryology, cytology, and genetics and his role in beginning the merger of these three fields into cell biology, and demonstrates his mastery of scientific reasoning and experimental design. A bibliography of Boveri's witings and his obituary notices are included. Beckner, Morton. The Biological Way of Thought. Berkeley: University of California Press, 1968; viii + 200 pp.; $5.95 clothbound, $1.95 paperbound. In this reissue of his thoughtful philosophical study of the methodology of biology, Professor Beckner sets forth his position that biology is more than the application of physicochemical laws to life processes, that it is a discipline with its own distinctive methods of concept formation and explanation. Bennison, Saul. Tom Rivers. Reflections on a Life in Medicine and Science. Cambridge, Mass.: MIT Press, 1967; xxi + 682 pp.; $17.50. Presented in the form of an oral history memoir tape-recorded in the months prior to his death, Dr. Rivers' autobiography provides us with a first account of the development of virology in the United States and with candid appraisals of the biomedical institutions and scientists with whom Dr. Rivers was associated during his long and eminent career in virology. Berry, William B. N. Growth of a Prehistoric Time Scale. San Francisco: W. H. Freeman and Co., 1968; viii + 158 pp., illus.; $5.75 clothbound, $2.50 paperbound. A study of interest to the historian of science and to those working in geology, paleontology, and evolutionary biology. Berry traces the development and use of a descriptive and an interpretive time scale based on the fossil record and the principles of organic evolution through natural selection. His account moves from the observations of eighteenth-century figures such as Hutton and Buffon to the new lines of research that have been opened in the 1960's by modifications in the use of shorter time units. Bradbury, S. The Evolution of the Microscope. Oxford: Pergamon Press, 1967; x + 357 pp. illus.; 80 S. Pointing out that 4"ofall the instruments used by the scientist, the microscope is perhaps the one which most aptly symbolizes this profession to the nonscientist," Bradbury examines the develop-

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The J. H. B. Bookshelf ment and use of the microscope in biology. His study, accompanied by a large number of excellent illustrations, takes us from the probable recognition of the magnifying properties of simple convex lenses in antiquity to the development of the ultraviolet and electron microscopes. Brunn, W. L. von. Kreislauffunktion in William Harvey's Schriften. Berlin, New York: Springer-Verlag, 1967; viii + 161 pp. A new study of Harvey's work on the circulation of the blood by the prominent German historian of medicine and science. Claude Bernard and Experimental Medicine. Collected papers from a symposium, Minneapolis, Minn., April 1965, and an English translation of Bernard's Cahier Rouge. Ed. Francisco Grande and Maurice B. Visscher. Cambridge, Mass.: Schenkman, 1967; 2 vols. in 1; 210 + vi + 120 pp., illus.; Clothbound, $8.95, paperbound, $4.95. The contents of this symposium, held to honor the centennial of the publication of Bernard's An Introduction to the Study of Experimental Medicine, include an introduction and summary by Grande and 13 papers that range from celebrations of Bemard and the Introduction to excellent historical analyses. The Cahier Rouge, translated by Hebbel Hoff and Lucienne and Roger Guillemin, is a previously unpublished Bernard notebook with entries covering the decade 1850-1860 which deal with a broad range of experimental and philosophical issues. Daniels, George H. American Science in the Age of Jackson. New York: Columbia University Press, 1968; xii + 282 pp.; $7.95. A study of the development of science in America in the thirty years following the War of 1812. Chapters 1 and 2 and appendices depict the emergence of an organized, professional scientific community in America, while chapters 3 through 9 examine the ideas about science and its pursuit prevalent among scientists and philosophers of science. WVhileDaniels says little about the science per se of the period, his chapter on "Science, Theology, and Common Sense" offers a broad background for students of the Darwinian controversy in America. Dannenfeldt, Karl H. Leonhard Rauwolf, Sixteenth-Century Physician, Botanist, and Traveler. Harvard Monographs in the History of Science. Cambridge, Mass.: Harvard University Press, 1968; viii + 321 pp., illus.; $7.95. Rauwolf, a Bavarian physician, was the first modern botanist to collect and describe the flora of the Near East, traveling in the Levant from 1573 to 1575 and publishing an account of his journey and work in 1582. Drawing upon Rauwolfs writings and upon the works of other Renaissance travelers, Dannen-

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feldt portrays the European's impression of the sixteenthcentury Moslem world, the nature of an early scientific field trip, and the pioneering botanical observations of a generally neglected figure in the history of botany. Darwin and Henslow. The Growth of an Idea: Letters 18311860. Ed. Nora Barlow. Berkeley: University of California Press, 1967; xii + 251 pp., illus.; $6.50. Lady Barlow, a granddaughter of Charles Darwin, has brought together a volume of correspondence which depicts Darwin's development as a scientist and shows us an important personal influence on that development in the person of John Stevens Henslow. Henslow, Professor of Botany at Cambridge, recommended Darwin's appointment as naturalist aboard the Beagle in the years 1831-1836. Frisch, Karl von. A Biologist Remembers. Trans. Lisbeth Gombrich. International Series of Monographs in History and Philosophy of Science, vol. I. Gen. Ed. M. Florkin and G. A. Kerkut. Oxford: Pergamon Press, 1967; ix + 200 pp.; $6.00. Although we learn little of von Frisch himself in this autobiography, it provides a fascinating account of his major discoveries in the language, behavior, and senses of the honeybee, and the biology, behavior, and senses of fishes, as well as a glimpse of life at German and Austrian universities over a half-century span. Gasking, E.izabeth. Investigations into Generation, 1651-1828. Baltimore: The Johns Hopkins Press, 1967; 196 pp., illus.; $6.00. Using Thomas Kuhn's concept of a paradigm as her model for historical analysis, Dr. Gasking examines investigations into sexual generation dating from the publication of Harvey's De Generatione in 1658 to von Baer's announcement of his discovery of the mammalian egg in 1828. A final chapter surveys studies of generation during the nineteenth and early twentieth centuries. Her analysis of work on the closely related questions of embryological development, spontaneous generation, regeneration of parts, and inheritance forms a superb case study on the historical interplay between biological theory and fact. Granit, Ragnar. Charles Scott Sherrington. An Appraisal. British Men of Science Series, Ed. Sir Gavin de Beer. London: Thomas Nelson and Sons, Ltd., 1967; xi + 188 pp., illus.; 42 S. Nobel Laureate Granit, once a student of Sherrington's, focuses on Sherrington's achievements at Oxford in the 1920's and their relevance to current neurophysiological research. Chapters are also devoted to Sherrington's personality and life, the historical background to his fundamental analyses of the

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The J. H. B. Bookshelf physiology of the central nervous system, and to his literary works. Historical Aspects of Microscopy. Ed. S. Bradbury and G. L'E Turner. Published for the Royal Microscopical Society. Cambridge, England: W. Heifer, 1967; 235 pp., illus.; 42 S. Originally delivered at a conference held by the Royal Microscopical Society, these six essays survey the technical and conceptual development of visual and microscopic optics from antiquity to the development of the electron microscope, including a description by Needham and Lu of early seventeenth-century Chinese optical instruments. Koestler, Arthur. The Ghost in the Machine. N.Y.: MacMillan, 1967; xiv + 384 pp.; $6.95. Following his treatment of scientific discovery and artistic inspiration in The Sleepwalkers and The Act of Creation, Koestler here offers a "psychological and evolutionary study of modern man's predicament" -his urge to self-destruction. The biologist and historian will find much food for thought and argument in Koestler's often witty and penetrating, but at the same time polemically unbalanced, critiques of evolutionary and psychological theories and his comments on genetics, the neurosciences, philosophy, history, and sociology. Lanham, Url. The Origins of Modern Biology. New York: Columbia University Press, 1968; x + 273 pp.; $6.95. Geared primarily for the student and general reader, Lanham's history ranges from Hippocratic medicine to the early twentiethcentury founding of genetics. The rise of genetics is the event which he feels marks the discernible start of modern biology, while Darwinism is viewed as the major event in the history of biology and biology's main contribution to the history of ideas. Following three introductory chapters on adaptiveness in living nature, the origin and uniqueness of man, and the nature of science, Lanham surveys Greek and Arabic biology, Roman and medieval science, the scientific renaissance, descriptive biology, evolutionary biology, the cell theory, and reductionism. G. Mendel Memorial Symposium, 1865-1965. Proceedings of a Symposium held in Brno, August 4-7, 1965. Ed. M. Sosa. Prague: Academia. Publishing House of the Czechoslovak Academy of Sciences, 1966; xxii + 287 pp. A series of 20 lectures and 11 discussions organized around the following themes: origin of Mendelism, establishment of genetics, modern development of genetics, and special application of genetics. Oppenheimer, Jane M. Essays in the History of Embryology

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and Biology. Cambridge, Mass.: MIT Press, 1967; ix + 374 pp.; $12.50. In these 13 essays, which move back in time from an examination of twentieth-century embryological concepts to the study of plant grafting described by William Gilbert in De Magnete, Professor Oppenheimer skilfully shows the relevance and fascination of the history of biology for the contemporary student, teacher, and investigator. Ramon y Cajal, Santiago. Recollections of My Life. Trans. E. Horne Craigie with the assistance of Juan Cano. Cambridge, Mass.: MIT Press, 1966; xi + 638 pp., illus.; $10.00. Cajal's autobiography is a major document for historians of the neurosciences, recording the life and work of the Spanish histologist and neuroanatomist whose fundamental researches included the establishment of the nerve cell and its processes as the functional unit of the nervous system. Originally published in 1937 by the American Philosophical Society, this MIT Press reissue should be welcomed by many historians and working biologists. Selye, Hans. In Vivo. The Case for Supramolecular Biology presented in Six Informal Illustrated Lectures. New York: Liveright, 1967; 168 pp., illus.; $5.95. Based upon lectures to medical students and physicians, Dr. Selye "pleads the cause of old-fashioned supramolecular biology" in a book which should engage the interests of general readers as well as those trained in the biomedical sciences. Exploring the nature of problem-finding and problem-solving, with the aid of examples from his own research on phenomena such as the general adaptation syndrome, he sets forth his belief that "no matter how much we shall learn about the most intimate mechanisms of biological phenomena, we will always need the old-fashioned holistic approach." In Vivo, together with Dr. Selye's earlier exploration of the philosophy, logic, and psychology of scientific investigation in From Dream to Discovery (New York: McGraw Hill, 1964), should be read in particular by any young person contemplating a career in biomedical research. Topsell, Edward, and T. Muffet. The History of Four-footed Beasts and Serpents and Insects. With a new introduction by Willy Ley. New York: DeCapo Press, 1967; 3 vols.: 620, 246, 270 pp., illus.; $65.00. Volume I of Topsell's Four-footed Beasts, the first major book on animals printed in English in Great Britain, was published in 1607 and was based upon Conrad Gesner's Historiae Animalium (1551-1558). Topsell drew upon Gesner for Vol. 2 as well, although this work did contain some new sections by Topsell; Muffet, similarly,

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The J. H. B. Bookshelf based his Insectorum sive Minimorum Animalium Theatrum (vol. 3, Insects) chiefly upon Gesner's classic work. This handsome issue of the Topsell and Muffet volumes by Da Capo Press, reprinted from the 1658 edition published in London, will provide hours of delightful reading for those interested in the history of zoology and descriptive biology. Watson, James. The Double Helix. New York: Atheneum, 1968; xvi + 238 pp., illus.; $5.95. As the subtitle informs the reader, Watson's widely reviewed best-seller is "a personal account of the discovery of the structure of DNA." For the scientist, historian, and layman, Watson's narrative offers a rare firsthand glimpse of the interplay of scientific work, persons and personalities, and circumstances which composed the fabric of a major biological discovery. Weiner, Dora B. Raspail, Scientist and Reformer. New York: Columbia University Press, 1968; xii + 336 pp., illus.; $11.00. The first scholarly study of Francois Vincent Raspail, a fascinating but generally unknown figure in French politics, science, and medicine of the 1820's to 1870's. Dr. Weiner focuses skilfully on the interplay in one man's life and thought between science, social reform, and politics. An excellent bibliography of books and manuscripts by, or relevant to, Raspail is included. Young, James Harvey. The Medical Messiahs. Princeton, N.J.: Princeton University Press, 1967; xiv + 460 pp.; $9.00. In this second volume of his study of health quackery in the U.S., the author of The Toadstool Millionaires examines medical quackery and self-dosage within the context of American society, government, science, and the marketing of health care products. It is estimated that Americans annually spend over $2 billion on quack cures and medicines; the paradox of the American people's irrationalism regarding health at a time of increasing scientific sophistication in medicine forms the central theme of Young's colorful and well-researched study in American social history. Histoire et biologie. Cahiers du cercle d'etude historique des sciences de la vie. Ed. Professor Jean-Frangois Leroy and Dr. J. Schiller. Fascicule 1 January, 1968. Laboratoire d'Ethnobotanique, Museum National d'Histoire Naturelle, 55 Rue Cuvier, Paris (5e). This first issue of some 45 pages is devoted to Vesalius, with papers and translations by P. Huard, L. Chauvois, and J. Schiller. The joumal will deal with historical problems found in the biological sciences and

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will relate them to today's biologist. Biographical and anecdotal details will be excluded. Attention will be paid instead to the development of research techniques and the evolution of ideas. Folia Mendeliana. Papers relating to Mendel and to the early development of genetics. Ed. Vftezslav Orel. Moravian Museum, Brno, Czechoslovakia. Issue No. 2, November 1967, 47 pp., illus. Included in this second issue of the Folia Mendeliana are papers in English and German by W. Coleman, F. Weiling and V. Orel, W. George, R. C. Olby, and L. Maranova, and a supplement to the Bibliographia Mendeliana published for the Mendel Memorial Symposium in Brno in 1965. Supplements to the Bibliographia will be published periodically in the Folia.

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Index to Volume I SPRING-FALL 1968

A

Biologist Remembers, K. von Frisch, review, 336. A Naturalist in Russia; Letters from Peter Simon Pallas to Thomas Pennant. Ed. C. Urness, review, 333. Adams, Mark B., "The Founding of Population Genetics: Contributions of the Chetverikoff School 1924-1934," 23-39. Agassiz, Louis, and Trigonia, 4851; views on inheritance and animal breeding, 182-196; lectures on "The Structure and growth of domesticated animals," 182-96; Bibliographia Zoologiae et geologiae, review, 333. "Agassiz, Mendel, and Heredity," J. A. Weir, 179-203. Agol, I. I., 24. Allen, Garland E., "Thomas Hunt Morgan and the Problem of Natural Selection," and 113-39; Dennis McCullough, "Notes on Source Materials: The Edwin Grant Conklin Papers at Princeton University," 325-31. Ambrosioni, F., and diabetic glycemia, 145. American Science in the Age of Jackson, G. H. Daniels, review, 335. Ancient Medicine. Selected Papers of Ludwig Edelstein, ed. 0. Temkin and C. L. Temkin, review, 333. Animal breeding, and views heredity in 19th century, 179-203. Animal life histories, by Leuwenhoek, 9-21. Animal populations, Leuwenhoek's

studies of, 3-9; studies of from Lamarck to Darwin, 225-259. Antagonistic muscle action, Sherrington's analysis of, 63-83. Aristotle, and ovism, 6. Astaurov, B. L., 27. "August Weismann and a Break from Tradition," F. B. Churchill, 91-112. Baer, K. E. von, definition of species, 166. Bailey, Liberty Hyde, and rediscovery of Mendelism, 208-216. Baltzer, Fritz, Theodor Boveri. The Life and Work of a Great Biologist, review, 333. Barreswil, Charles-Louis, 144. Bates, Henry Walter, travels with Wallace, 265-69. Bateson, William, and discontinuous variation, 117-18. Beckner, Morton, The Biological Way of Thought, review, 334. Barbara G., "Wallace, Beddall, Darwin, and the Theory of Natural Selection," 261-323. Bell, Charles, 64. Beneden, Edouard von, 103, 106. Bennison, Saul, Tom Rivers. Reflections on a Life in Medicine and Science, review, 334. Bernard, Claude, and glycogenic function of liver, 144-54. Berry, William B. N., Growth of a Prehistoric Time Scale, review, 334. Bibliographiae Zoologiae et geologiae, L. Agassiz, review, 333. Biogeography, preDarwinian views on, 230-32.

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INDEX TO VOLUME I Biological species concept, origin of, 163-177. Biophors, in germ-plasm theory, 108-10. Bradbury, S. The Evolution of the Microscope, review, 334. Brocchi, G. B., and species extinction, 235. Brooks, W. K., 137; and E. G. Conklin, 326, 330. Brunn, W. L., Kreislauffunktion in William Harvey's Schriften, review, 335. Buffon, definition of species, 164165. Cairns, J., G. S. Stent, and J. D. Watson, ed., Phage and the Origins of Molecular Biology, Essay review by R. C. Lewontin, 155-61. Candolle, Augustin-Pyramus de, and plant geography, 231-32. Castle, W. E., and H. MacCurdy, experiments on selection, 11920. Catastrophism, and Trigonia, 51-55. Charles Scott Sherrington, R. Granit, review, 336. Chetverikov, S. S., 23. Chetverikov School, The, 23-29. Churchill, Frederick B., "August Weismann and a Break from Tradition," 91-112. Claude Bernard and Experimental Medicine, ed. F. Grande and M. B. Visscher, review, 335. Common path, Sherrington's principle of, 78-80. Conklin, E. G., 113; personal papers of, 325-31. Correns, Carl, 205, 215. Cuvier, Georges, and species extinction, 227-28. Daniels, George H., American Science in the Age of Jackson, review, 335. Karl H., Leonhard Dannenfeldt, Rauwolf, review, 335. Darwin, Charles, and Trigonia, 5155; ideas on animal demography and species, 242-59; joint paper with Wallace, 261, 299-311; relations and correspondence with Wallace, see Wallace. Darwin and Henslow. The Growth

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of an Idea, ed. N. Barlow, review, 336. Darwinian theory, opposition to, 114-16. Decerebrate rigidity, Sherrington's work on, 70-71. Demography, animal, Leuwenhoek's work, 1-22; pre-Darwinian theories, 227-42; Darwin's views, 242-59. Descartes, Rene, 64. D'Orbigny, Alcide, 52. Dobzhansky, Th., 23. Driesch, Hans, 109. Drosophilia, first genetic analysis of free-living, 24, 30-35; mutant, T. H. Morgan's work with, 12836. Dubinin, N. P., 23. "Editorial foreword," iii-iv. Egerton, Frank N., "Leuwenhoek as a Founder of Animal Demography," 1-22; "Studies of Animal from Lamarck to Populations Darwin," 225-59. Elton, Charles, Animal Ecology, 225. Epigenesis, and germ-plasm theory, 104-11. Essays in the History of Embryology and Biology, J. Oppenheimer, review, 337. Essentialist species concept, 163. Evolution, and teleology, 124-26; and Mendelism, 125-128. Evolutionary process, Chetverikov's statement of, 33-37. "First steps in Claude Bernard's Discovery of the Glycogenic Function of the Liver," M. D. Grmek, 141-54. Fleming, John, 236. Flemming, Walther, 103. Flourens, Pierre, 58. Focke, W. G., and Mendel's rediscovery, 211. Folia Mendeliana, review, 340. Forbes, Edward, and biotic community concept, 240-42; theory of polarity, and Wallace, 279. Foster, Michael, 58. Frisch, Karl von, A Biologist Remembers, review, 336.

INDEX TO VOLUME

C. Mendel Memorial Symposium, 1865-1965, ed. M. Sosa, review, 337. Gaimard, J., 43. Galapagos Islands, and Wallace's theory of natural selection, 27476, 285-86. Gaskell, Walter, 59. Gasking, Elizabeth, Investigations into Generation, review, 336. Gene interaction, concept of, 13336. Generelle Morphologie, E. Haeckel, 94-99. Genetics, population, 23-29. Genetics, problems in history of, 180-81. Genotypic milieu, development of concept of, 28-33, 38. Germ-plasm theory, Weismann's, 91-1 12. Giebel, C. G., 53. Goltz, Friedrich, 59. Gray, Asa, and Agassiz, 182. Grmek, M. D., 'First Steps in Claude Bernard's Discovery of the Glycogenic Function of the Liver," 141-54. Gould, Stephen Jay, "Trigonia and the Origin of Species," 41-56. Granit, Ragnar, Charles Scott Sherrington, review, 336. Graunt, John, 2. Growth of a Prehistoric Time Scale, W. Berry, review, 334. Haeckel, Emst, and germ-plasm theory, 93-112. Hale, Matthew, population studies, 240. Hall, Marshall, 58. Hardy, G. H., 24. Harrison, Ross G., 113. Held, Hans, 67. Hellwig, J. C. L., 167. Heredity, theory of, and Darwinism, 115-36. Hertwig, Oscar, and spermatogenesis, 107-08. Histoire et biologie. Cahiers du cercle d'etude historique des sciences de la vie, review, 339. Historical Aspects of Microscopy, ed. S. Bradbury and G. L'E Turner, review, 337. Hooker, Joseph D., and Darwin-

I

Wallace papers, 261, 300-03, 305-07, 310, 317-18. Humboldt, A. von, and plant geography, 230. Hybridization of apple trees, Mendel's program for, 219-24. "IlUger and the Biological Species Concept," Ernst Mayr, 163-77. Illiger, Johann C. W., essay on the species, 168-77. Illustriertes Handbuch der Obstkunde, Mendel's notes in, 219, 220. In Vivo, H. Selye, review, 338. Integrative Action of the nervous system concept, development of, 57-89. Investigations into Generation, E. Gasking, review, 336. Jannsens, F. A., chiasmatype theory, 133. Jenkins, Fleeming, 118. Jenkins, F. M., 54. Johannsen, W., pure-line experiments, 134. Journal of the history of biology, scope of, iii-iv. Kant, definition of species, 166-67. Koch, Robert, 59. Koestler, Arthur, The Ghost in the Machine, review, 337. Koltsov, N. K., 27. Kreislauffunktion in William Harvey's Schriften, W. L. Brunn, review, 335. Lamarck, J. B., and Trigonia, 4346; and evolution of species, 22830. Lamarckism, and natural selection, 114, 121-22; and Wallace's theory of natural selection, 272, 274, 277-78, 280, 284. Langley, John N., 59. Lanham, Url, The Origins of Modern Biology, review, 337. Leonhard Rauwolf, D. H. Dannenfeldt, review, 335. Leuckart, Rudolph, 91. "Leuwenhoek as a Founder of Animal Demography," F. N. Egerton, 1-22. Lewontin, R. C., essay review of

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INDEX TO VOLUME I Phage and the Origins of Molecular Biology, 155-61. Liebig, Justus von, 180. Linnaeus, and essentialist species concept, 163. Linnean Society of London, and Darwin-Wallace papers, 261, 30103, 317-18. Liver, discovery of glycogenic function of, 141-54. Lyell, Charles, on species concept and population biology, 232-40; and development of Wallace's theory of natural selection, 27173, 276-78, 280, 283-87, 295, 313-14. MacCurdy, H., see Castle, W. E. McCoy, Frederick, 54. McCullough, Dennis, see Allen, G. Magendie, Francois, and glycemia, 146. Malthus, and population pressure, 226. Mayr, Ernst, "IlUger and the Biological Species Concept," 163-77. Everett, "Editorial Mendelsohn, Foreword," iii. Mendel, Gregor, Brunn lectures on 178-99; experiments, Pisum mice breeding work by, 200-02. Mendelian principles, and evolution, 125-28. Mendelism, rediscovery of, 205-18. "Mendel's Program for the Hybridization of Apple Trees," V. Orel and M. Vivra, 219-24. Mivart, St. George, 120. Mobius, Karl A., and biotic community concept, 241. Morgan, T. H., and natural selecand Weismann, tion, 113-39; 122-24; view of scientific methodology, 122-24; on teleology and evolution, 124-25; students of, 136-37; and acceptance of genetics, 180-81; and E. G. Conklin, 326-27. Museum of Comparative Zoology, Harvard, 179. Mutation theory, of deVries, 12728. Nageli, C., and Mendel, 199-200. Natural Selection, T. H. Morgan and, 133-39; and Darwin and Wallace, 261-323.

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Neotrigonia, see Trigonia. Neurone theory, 66-69. Nilsson-Ehle, H., 135. Nominalist species concept, 163. "Notes on Source Materials: The Edwin Grant Conklin Papers at Princeton University," G. Allen and D. McCullough, 325-31. Oldenburg, Henry, 3. Ontogeny, Haeckel's definition of, 96-97. Oppenheimer, Jane M., Essays in the History of Embryology and Biology, review, 337. Orel, V. and M. Vivra, "Mendel's Program for the Hybridization of Apple Trees," 219-24. Overgrowth principle, Haeckel's, 97-100; Weismann's view of, 101-02, 104. Pangensis, and germ-plasm theory, 105-10; and deVries' rediscovery of Mendelism, 207. Parkinson, James, and Trigonia, 46-48. Pasteur, Louis, 180. Pearson, Karl, 24. Peron, P., 42. Phage and the Origins of Molecular Biology, ed. J. Caims, G. S. Stent, and J. D. Watson. Essay review by R. C. Lewontin, 155-61. Philipchenko, I. A., 25. Plant-Breeding, L. H. Bailey, 20809. Pliny, 13. Population genetics, experimental, 23-29. Preformation theory, 6. Proprioceptive system, Sherrington's concept of, 81-82. Quoy, J., 43. Rabl, Karl, 103. Ram6n y Cajal, Santiago, 66; Recollections of My Life, review, 338. Rapoport, I. A., 24. Raspail, Scientist and Reformer, D. B. Weiner, review, 339. Ray, John, definition of species, 165-66. Reciprocal innervation, Sherrington's analysis of, 71-77.

INDEX TO VOLUME I Terminologie, by J. C. W. Ifliger, 167-68. The Biological Way of Thought, M. Beckner, review, 334. The Double Helix, J. Watson, review, 339. The Evolution of the Microscope, S. Bradbury, review, 334. "The Founding of Population Genetics: Contribution of the Chetverikoff School 1924-1934," M. B. Adams, 23-39. The Germ-Plasm, a Theory of Heredity, by Weismann, 105. Sanders-Ezn, H., 70. The Ghost in the Machine, A. KoestSchwann, T., cell theory of, 92-93. ler, review, 337. Scientific methodology, T. H. MorThe History of Four-footed Serpents gan on, 122-24. and Beasts and Insects, E. Topsell Scoresby, William, 4. Scratch reflex, Sherrington's analyand T. Muffet, review, 338. sis of, 77-84. The Integrative Action of the Nervous System, by C. S. Sherrington, Selye, Hans, In Vivo, review, 338. 84-88. Serebrovsky, A. S., 25-26. "The J. H. B. Bookshelf," J. P. Setchenov, Johann, 66. Sherrington, C., anatomical work, Swazey, 333-40. 60-63. The Medical Messiahs, J. H. Young, "Sherrington's Concept of Integrareview, 339. tive Action," J. P. Swazey, 57-89. The Origins of Modern Biology, Smith, William, 42. U. Lanham, review, 337. "The Role of Liberty Hyde Bailey Species, origin of, and Trigonia, 41-56; T. H. Morgan's view of, and Hugo de Vries in the Redis116-17; concepts of, 163-77; covery of Mendelism," C. Zirkle, 205-18. pre-Darwinian ideas on extinction vs. evolution, 227-30; definition Theodor Boveri. The Life and Work of, and Wallace's theory of naturof a Great Biologist, F. Baltzer, al selection, 281. review, 333. Spermatogenesis, Hertwig's study "Thomas Hunt Morgan and the of, 107-08. Problem of Natural Selection," Spinal cord, reflex functions of, G. E. Allen, 113-39. 63-89. Timofeev-Resovsky, N. V., 23. Stomps, Th. J., and deVries' redisTom Rivers. Reflections on a Life covery of Mendel, 215. in Medicine and Science, S. BenStrasburger, Edward, 103. nison, review, 334. "Studies of Animal Populations Topsell, E., and T. Muffet, The Hisfrom Lamarck to Darwin," F. N. tory of Four-footed Beasts and Egerton, 225-59. Serpents and Insects, review, 338. Townsend, Joseph, 235. Swainson, William, and biogeography, 230; Treatise on Geogra"Trigonia and the Origin of Spephy, and Wallace, 270-71. cies," S. J. Gould, 41-56. Swammerdam, Jan, 13. Trigonia, discovery of, 42-43, 52Swazey, Judith P., "Sherrington's 55. Concept of Integrative Action," Tschermak, Erik von, 205. 57-89; "The J. H. B. Bookshelf," 333-40. Ulloa, Antonio de, 235. Synapse, introduction of term by Variations, and natural selection, Sherrington, 67-69. 114, 117-36. Teleology, and evolution, 124-25. Vavilov, N. I., 25.

Recollections of My Life, S. Ram6n y Cajal, review, 338. Reflex inhibition, Sherrington's work on, 65-84. Redi, Francesco, 13. Reproductive potentials, Leuwenhoek's calculations of, 22. Reticular theory, of von Gerlach and Golgi, 66. Roberts, H. F., letters to by Mendel's rediscoverers, 206-07. Roux, Wilhelm, 103.

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INDEX TO VOLUME I Vivra, M., see Orel. Virchow, Rudolph, 54. de Vries, Hugo, and pangenesis, 105, 108; and origin of variations, 125-28; rediscovery of Mendelism, 205-18. Wallace, Alfred R., 236; joint paper with Darwin, 261, 299-311; scientific training and voyages, 26369; "On the Law which has regulated the Introduction of New Species," analysis of, 269-80; "Note on the Theory of Pernanent and Geographical Varieties," analysis of, 280-89; correspondence and relations with Darwin, 276, 282, 289-317; tabulation of letters on Darwin-Wallace papers, 319-23; "On the Tendency of Varieties to depart indefinitely from the Original Type," 294-97, 299-311. "Wallace, Darwin, and the Theory

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of Natural Selection," B. G. Beddall, 261-323. Wallace, William, 263, 265. Watson, James, The Double Helix, review, 339. Weiner, Dora B., Raspail, Scientist and Reformer, review, 339. Weir, J. A., "Agassiz, Mendel, and Heredity," 179-203. Weismann, August, germ-plasm theory of, 91-112; and T. H. Morgan, 122-24. Whytt, Robert, 65. Wilson, Edmund, B., criticism of Roux-Weismann theory, 111-12. Winslow, J. B., 64. Wright, Sewall, 26. Young, James H., The Messiahs, review, 339.

Medical

Zirkle, Conway, "The Role of Liberty Hyde Bailey and Hugo de Vries in the Rediscovery of Mendelism," 205-18.