Darwinism to-day : a discussion of present-day scientific criticism of the Darwinian selection theories, together with a brief account of the principal other proposed auxiliary and alternative theories of species-forming

Preface

This book is written for the sake of presenting simply and concisely to students of biology and to general readers the present-day standing of Darwinism in biological science, and to outline for them the various auxiliary and alternative theories of species-forming which have been proposed to aid or to replace the selection theories.

Our actual knowledge of the factors and mechanism of organic evolution and our hypotheses and theories which serve to fill in the present gaps in this knowledge have been greatly added to and modified in the last few years. Much that the general reader includes in his conception of organic evolution, based on his reading of Darwin and Wallace and Spencer, has been materially modified and some of it proved untenable by modern investigation ; while much which had no place in this earlier general understanding of evolutionary method and process may now be confidently added to it. The present time is one of unprecedented activity and fertility both in the discovery of facts and in attempts to perceive their significance in relation to the great problems of bionomics. Both destructive criticism of old, and synthesis of new hypotheses and theories, are being so energetically carried forward that the scientific layman and educated reader, if he stand but ever so little outside of the actual working ranks of biology, is likely to lose his orientation as to the trend of evolutionary advance. Precisely at the present moment is this modification of the general point of view and attitude of philosophical biologists unusually important and far-reaching in its relation to certain long-held general conceptions of biology and evolution. This modification of the general trend of evolutionary thought must also necessarily

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IV

PREFACE.

strongly affect our conceptions of the underlying principles of such correlated sciences as sociology, pedagogy, etc. It is, then, as a means of orientation in evolutionary matters for the general reader and for the unspecialised but interested student of science that this book is prepared.

That it may not be without some special usefulness to more advanced students and biological workers there are added, in appendices to the chapters, special notes (referred to in the text by small super-numbers) in which are given numerous exact references to general or special books or papers, and accounts, in more or less detail, of particular observations, experiments, or theoretical discussions, as well as references to extended bibliographic lists of the subjects under treatment. These notes will enable students, or others interested, to look up the original sources of our knowledge of the subjects of the various chapters, and to find more detailed general or special discussions of them than can be given in this book. These notes also enable the author to introduce into the book some details of his own observations and experiments touching various evolutionary subjects.

V. L. K.

Stanford University, June , igo 7.

Chapter I. Page

INTRODUCTORY: THE “DEATH-BED OF DAR- WINISM” i

Modern activity in biologic study, i. Darwinism not synonymous with evolution, 3. Present-day anti-Darwinism, 4. Intemperate anti-Darwinism, 6. Outline of this book, 7.

Appendix: Dennert’s intemperate attack on Darwinism,

7. An anti-evolution university biologist, 8. Friedmann’s theory to replace evolution with divergence, 8.

Chapter II. Darwinism And Evolution Defined And

DISTINGUISHED 10

Animal and plant kinds originate in one of three ways,

10. The theory of descent defined, 11. The theory of descent given validity by Darwin’s explanation of the cause of it, 12, Darwinism defined and analysed into its fundamental assumptions and facts, 13. Sources of scientific evidence for the theory of descent, 17. Relation of theology, philosophy, pedagogy, and sociology to the theory of descent, 20.

Appendix: Accounts of history of the descent theory,

22. Books giving the evidences for descent, 23. Discussions of the relation of descent and theology, 23. Discussions of the relations of biology and philosophy, 24. Biology and sociology, 24.

Chapter III

The attack of the theologians, 25, The present-day attack of the scientific men, 25. Some of the principal objections to natural selection summarised, 30. Darwinian or fluctuating variations too small to serve as “handles”

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VI

CONTENTS.

for natural selection, 36. Many specific differences are indifferent, i. e., not adaptive, 38. The extinguishing of the extreme variations by interbreeding, 44. The improbability of the occurrence of the right variations at the right time, 45. The difficulty of explaining the production by natural selection of specialisations useful only in highly complex condition, 49. The objection based on the over-development of specialisations, 53. The objection based on insufficient time, 54. The objection that natural selection tends to preserve the type rather than the variants, and hence opposes change, 56.

Appendix: Books and papers on variation, 57. Cases of marked variation in parthenogenetic animals, 58. Variation according to the law of probabilities, 59. Quetelet, the discoverer of variation according to the laws of chance, 61. Example of trivial variations, 62. Nageli’s seven objections to species-forming by selection, 62. Wolff’s, attack on the selectionists’ assumption of the appearance at the right time of the needed variation, 64. Example of non-correlated variability in bilaterally repeated organs, 65. Henslow’s antagonism to selection as an explainer of floral correlations, 67. Wolff’s objection to the necessary assumption of identical and coincident variation in repeated structures, as feathers, scales, etc., 67. Example of mal-adaption in the egg-laying habit of Phryganidia calif ornica , 68 — Pieper’s antagonism to the selection explanation of colour and pattern in insects, 69.

CHAPTER IV. DARWINISM ATTACKED ( Continued )

Objection to the exclusively linear or quantitative character of the fluctuating or Darwinian variations, 70. Galton’s law of regression, 71. Selection may produce evolution (continuous change) but not species (discontinuous series), 73. Pfeffer’s objection based on the slowness of species transformation, 75. The difficulty of explaining the sterility of species by selection, 76. Selection cannot explain extreme or complete degeneration of useless parts, 77. Objections to the assumed rigour of the struggle for existence and to the actuality of intra-specific or personal selection, 79. Indiscriminate extermination due to the fortune of position and time, 80. The necessity of sexual

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selection, a discredited theory, for the support of the natural selection theory, 85. Natural selection rests on an unwarranted assumption of its homology with artificial selection, 86. Many biologists find natural selection unable to account for known biologic conditions, 89. Significance of the concessions of Darwinians, 90. Korschinsky’s extreme anti-Darwinian doctrine, 91. Delage’s “true role of selection,” 93. Morgan’s rejection of natural selection as a species-forming factor, 93.

Appendix: Galton’s statement of the law of regression,

97. Wolff’s criticism of panmixia, 98. Example of ineffective panmixia, 100. Example of progressive degeneration inexplicable by natural selection, 100. Wolff’s discussion of the selection coefficient, 101. Example of non-selection of trivial differences, 103. References to books and papers on plant breeding, 105.

CHAPTER V. DARWINISM ATTACKED ( Continued ): THE THEORY

OF SEXUAL SELECTION 106

Secondary sexual differences or characters, 107. Classification of secondary sexual characters, 107. Useless and harmful characters not explicable by natural selection, no. Theory of sexual selection to account for them: the theory defined, in. Darwin’s assumptions as basis of the theory of sexual selection, 112. Difficulties in the way of a general application of the theory, 113. The theory applicable only to species in which males are more numerous than females, 113. The passivity of females, 114. Males of species in which no real pairing occurs also show striking secondary sexual characters, 114. Necessity of assuming unproved aesthetic development among lower animals, 114. Few recorded cases of observed choosing by female, 115. Difficult to assume utility for many secondary sexual characters, 115. Stolzmann’s case of the Andean humming-birds, 116. How explain the beginnings of secondary sexual characters, 117. How explain ornamental characters appearing in both males and females,

1 18. Morgan’s objections to sexual selection theory, 118. Experimental evidence touching the theory is against it,

120. Mayer’s experiments with Promethea and Porthelria moths, 121. Douglass’s and Diirigen’s observations on

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PAGE

lizards, 123. Substitutionary theories of the origin of secondary sexual characters, 124.

Appendix: References to books and papers discussing sexual selection, 125. Wolff’s critical exposition of weaknesses in sexual selection, 126.

Chapter VI

Position of the defenders of Darwinism, 129. Reaction against the too speculative positions of Haeckel and Weismann, 130. “Haeckelismus,” 130. Weismannism,

131. Struggle between Neo-Darwinians and Neo-Lamarckians, 133. Concessions of the Neo-Darwinians, 134. Answer to objection concerning the too slight character of fluctuating or Darwinian variations to serve as handles for natural selection, 138. Answer to the objection concerning the linear and quantitative character of Darwinian variation, 139. Answer to the objection that selection cannot produce many-branched descent, 142. Answer to the statement that selection can produce continuous change or evolution, but not species, 143. Answer to the objection concerning the production by selection of co-adaptive and highly complex specialisations, 144. Answer to the -objection concerning the over-development of specialisations, 146. Discussion of the difficulty that natural selection has with structural degeneration, 146. The Darwinian answer to the expressions of doubt about the rigour of selection, 148. Answer to the objections to the sexual selection theory, 148. Discussion of the objection to the derivation of evidence for natural selection from the facts of artificial selection, 150. Tayler’s general defence, 153.

Appendix: Weldon’s experiments on Carcinus , 158.

Tayler’s explanation of degeneration by natural selection,

162. Plate’s explanation of character fixity in domestic animals, 163.

CHAPTER VII. DARWINISM DEFENDED ( Continued ): PLATE’S CON- CILIATORY DEFENCE 164

Plate, a fair-minded Darwinian champion, 164. Answers to the objection based on the slight character and inutility of Darwinian variations, 165. Many slight differences at

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first glance apparently indifferent in character found on more careful inspection to be of advantage, 166. Slight characters aided by co-related differences, 167. The principle of the change of function, 168. Characters of indifferent value under one condition of environment, suddenly made important by a change in life-conditions,

169. Organs of universal character which can become modified in various directions, 169. Lamarckian factors called to the aid of Darwinism, 170. Answers to the objection based on the improbability of the appearance of the right variations at the right time for the progressive perfecting or development of an organ, 170. Selection directs itself according to variation, not variation according to any assumed needs of selection, 171. Selection works with plural variations, not single ones, 172. The same selective value can often be attained through combinations of various peculiarities and the same effect reached by various means, 172. The element of chance not peculiar to the Darwinian explanation of co-adaptations, 175. Answers to the objection based on the assumed improbability that during the course of the development of a complex organ or whole body-part, or during the perfecting of a changing adaptation the numerous necessary adaptations will occur in such a successive series as to make possible any harmonious correlation of the various single variations, 176. Plate’s reliance on the Lamarckian factor of the inheritance of characters acquired through use, disuse, and other functional stimuli,

178. The attainment of selective value by various means,

178. Weismann’s theory of germinal selection unacceptable, 180. Weismann’s principle of amphimixis of great importance, 180. The necessity of concessions admitted 181. The necessity of invoking auxiliary or aiding principles to support the natural selection theory, 182.

Appendix: Conn’s discussion of selective value, 182. References to papers on correlation, 184. Cope’s proof that natural selection cannot originate new characters, 185.

Chapter VIII

OTHER THEORIES OF SPECIES-FORMING: THEO- RIES AUXILIARY TO SELECTION .... 187

The presentation of theories to aid the selection theories or others to replace them really a continuation of the

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PAGE

defence of, and attack on, Darwinism, 187. The Weismannian theories, 188. Panmixia, 190. The theory of germinal selection, 193. The physical and chemical structure of protoplasm, 194. Objections to the theory of germinal selection, 200. Roux’s theory of intra-selection, or the battle of the parts, 201. Objections to Roux’s theory, 203. The theory of organic selection, or orthoplasy, 208.

Appendix: List of Weismann’s evolution papers, 212. Theories of ultimate protoplasmic structure, 214. Encasement theory, 215. Micromeric theories, 215. Buffon’s theory, 216. Spencer’s theory, 217. Darwin’s theory,

218. Nageli’s theory, 219. De Vries’s theory, 220. Hatschek’s theory, 222. Delage’s criticisms, 224. Le Dantec’s criticisms, 224. Verworn’s biogen hypothesis, 225. Delage’s machine theory, 225. Le Dantec’s theory of chemism, 225. Neo-vitalism, 226. Morgan’s criticism of Weismann’s method of argument, 229. References to discussions of orthoplasy, 229.

CHAPTER IX. OTHER THEORIES OF SPECIES-FORMING ( Continued )

THEORIES AUXILIARY TO SELECTION ( Continued ) 232

Isolation theories, 232. Wagner’s “Separations-theorie,”

234. Jordan’s upholding of the importance in species-forming of geographic isolation, 237. Biologic and sexual isolation, or physiological selection, 243. Gulick’s work and conclusions, 249.

Appendix: References to discussions of isolation, 253. Haacke’s summary of Wagner’s theory, 253. Grinnell’s studies of geographic differences in the chickadee, 255. Further references to discussions of isolation, 261.

Chapter X

OTHER THEORIES OF SPECIES-FORMING (Continued): THEORIES ALTERNATIVE TO SELEC- TION 262

Three general groups of theories proposed to replace the selection theories as explanations of species-forming and evolution, 262. The Lamarckian theory, 262. Objections to the Lamarckian factors, especially that of the inheritance

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PAGE

of acquired characters, 266. Great use could be made of the Lamarckian factors in explaining evolution phenomena if these factors could be given validity, 271. Orthogenesis and determinate variation, pointing toward orthogenesis,

271. Nageli’s theory of orthogenesis, 277. Eimer’s orthogenetic theory, 282. Cope’s theory of bathmism and kinetogenesis, 285. Jaeckel’s theory of metakinesis, 289.

Appendix: References to Lamarck’s writings, 290. Brown- Sequard’s experiments on guinea pigs, 290. Hyatt’s studies of Planorbts , 295. Fischer’s experiments with butterflies, 296. Experiments with silkworms, 298. References to books and papers on inheritance of acquired characters, 305. Redfield’s position, 305. Montgomery’s explanation of inheritance of variation, 306. Scientific aspects of Burbank’s work, 310. Orthogenetic variation in palaeontology, 319. A case of apparent determinate variation, 319. Pfeifer’s theory of orthogenesis, 320. Eimer’s theory of orthogenesis, 321. Apparent determinate evolution, 322. Snodgrass’s observances on bills of Galapagos birds, 323. Cope’s belief in orthogenetic evolution, 323. Whitman’s belief in determinate variation, 325. Cunningham and orthogenesis, 326.

Chapter XI

OTHER THEORIES OF SPECIES-FORMING (Continued): THEORIES ALTERNATIVE TO SELEC- TION ( Continued ) 327

Heterogenesis or the mutations theory, 327. Formulations of heterogenesis theories by von Kolliker, Dali, Galton, and Emery, 330. Korschinsky’s heterogenesis theory, 333. De Vries’s mutations theory, 337. Present status of de Vries’s theory, 348. Alternative theories to explain secondary sexual characters, 352.

Appendix: Mendel and his work, 356. References to recent work on Mendelism, 357. Darwin’s examples of race origin from sports, 357. A recent example of race origin from a sport in cattle, 358. Galton’s discussion of specific stability, 360. References to discussions by de Vries of species-forming, 362. American opinions of the mutations theory, 362. Davenport’s example of species origin by slight continuous change, 367. Merriam’s criticism of the mutations theory, 367. Plate’s criticism of the

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mutations theory, 368. References to theories explaining secondary sexual characters, 373.

Chapter XII. Darwinism's Present Standing

Natural selection the final control in evolution, but not a sufficient explanation of species-forming, 374. Weaknesses of the substitutionary theories, 375. The unknown factors of evolution, 377. Prime needs of evolution study; first, the intensive study, statistical and experimental, of variability, 378. Second, the means of cumulating variability along definite lines, 379. Third, the investigation of adaptation, 380. A suggested argument for a belief in the transference of ontogenic changes into phylogeny, 382. A suggested automatic causal factor of variability, purposive but not purposeful, 384. Our present ignorance and the call to work, 387.

Appendix: Wigand's criticism of the selection theories, 387. Lankester’s upholding of Darwinism, 389. De Vries’s discussion of species-forming by selection, 389. Delage’s estimate of selection, 390. Osborn’s championship of the unknown factors of evolution, 391. Klebs’s conclusions from experiments on plants, 392. Friedlander’s discussion of adaptation, 392. Loeb’s attitude toward the problem of species-forming, 393.

DARWINISM TO-DAY.

Chapter I. Introductory: The “death-bed Of Darwinism.”

“Vom Sterbelager des Darwinismus !” This is the title of a recent pamphlet 1 lying before me. But ever since there has been Darwinism there have been occasional deathbeds of Darwinism on title pages of pamphlets, addresses, and sermons. Much more worth consideration than any clerical pamphlets or dissertations, under this title, by frischgebackenen German doctors of philosophy — the title alone proving prejudice or lack of judgment or of knowledge — are the numerous books and papers which, with less sensational headlines but infinitely more important contents, are appearing now in such numbers and from such a variety of reputable sources as to reveal the existence among biologists and philosophers of a widespread belief in the marked weakening, at least, if not serious indisposition, of Darwinism. A few of these books and papers from scientific sources even suggest that their writers see shadows of a death-bed.

The present extraordinary activity in biology is twophased ; there is going on a most careful re-examination or Modem activ scrutiny of the theories connected with organic ity in biologic evolution, resulting in much destructive criticism of certain long-cherished and widely held beliefs, and at the same time there are being developed and almost feverishly driven forward certain fascinating and fundamentally important new lines, employing new methods,

DARWINISM TO-DAY.

of biological investigation. Conspicuous among these new kinds of work are the statistical or quantitative study of variations and that most alluring work variously called developmental mechanics, experimental morphology, experimental physiology of development, or, most suitably of all because most comprehensively, experimental biology.2 This work includes the controlled modification of conditions attending development and behaviour, and the pedigreed breeding of pure and hybrid generations. Now this combination of destructive critical activity and active constructive experimental investigation has plainly resulted, or is resulting, in the distinct weakening or modifying of certain familiar and long-entrenched theories concerning the causative factors and the mechanism of organic evolution. Most conspicuous among these theories now in the white light of scientific scrutiny are those established by Darwin, and known, collectively, to biologists, as Darwinism.

To too many general readers Darwinism is synonymous with organic evolution or the theory of descent. The word is not to be so used or considered. Darwinism, white mb**' primarily, is a most ingenious, most plausible,

and, according to one’s belief, most effective or most inadequate, causo-mechanical explanation of adaptation and species-transforming. It is that factor which, ever since its proposal by Darwin in 1859, has been held by a majority of biologists to be the chief working agent in the descent, that is, the origin, of species. However worthy Darwin is of having his name applied directly to the great theory of descent — for it was only by Darwin’s aid that this theory, conceived and more or less clearly announced by numerous pre-Darwinian naturalists and philosophers, came to general and nearly immediate acceptance — the fact is that the name Darwinism has been pretty consistently applied by biologists only to those theories practically original with Darwin which offer a mechanical explanation of the accepted fact of

INTRODUCTORY: “DEATH-BED OF DARWINISM.” 3 descent. Of these Darwinian theories the primary and all-important one is that of natural selection. Included with this in Darwinism are the now nearly wholly discredited theories of sexual selection and of the pangenesis of gemmules. It may also be fairly said that the theory of the descent of man from the lower animals should be included in Darwinism. For Darwin was practically the first naturalist bold enough to admit the logical and obvious consequences of the general acceptance of the theory of descent, and to include man in the general chain of descending, or ascending, organisms. So that the popular notion that Darwinism is in some way the right word to apply to the doctrine that man has come from the monkeys is rather nearer right than wrong. But biologists do not recognise the descent of man as a special phase of Darwinism, but rather of the whole theory of descent, or organic evolution.

Darwinism, then, is not synonymous with organic evolution, nor with the theory of descent (which two phases are D .. used by the biologist practically synonymously), not synonymous Therefore when one reads of the “death-bed of with evolution. Darwinism/’ it is not of the death-bed of organic evolution or of the theory of descent that one is reading. While many reputable biologists to-day strongly doubt the commonly reputed effectiveness of the Darwinian selection factors to explain descent — some, indeed, holding them to be of absolutely no species-forming value — practically no naturalists 3 of position and recognised attainment doubt the theory of descent.4 Organic evolution, that is, the descent of species, is looked on by biologists to be as proved a part of their science as gravitation is in the science of physics or chemical affinity in that of chemistry. Doubts of Darwinism are not, then, doubts, of organic evolution. Darwinism might indeed be on its death-bed without shaking in any considerable degree the confidence of biologists and natural philosophers in the theory of descent.

DARWINISM TO-DAY.

But the educated reader, the scientific layman, the thinker and worker in any line of sociologic, philosophic, or even

„ , theologic activity is bound to be disturbed and

Present-day

anti-Darwin- unsettled by rumours from the camp of pro-

lsm' fessional biologists of any weakness or mortal

illness of Darwinism. We have only just got ourselves and our conceptions of nature, of sociology and philosophy, well oriented and adjusted with regard to Darwinism. And for relentless hands now to come and clutch away our foundations is simply intolerable. Zum Teufel with these German professors ! For it is precisely the German biologists who are most active in this undermining of the Darwinian theories. But there are others with them ; Holland, Russia, Italy, France, and our own country all contribute their quota of disturbing questions and declarations of protest and revolt. The English seem mostly inclined to uphold the glory of their illustrious countryman. But there are rebels even there. Altogether it may be stated with full regard to facts that a major part of the current published output of general biological discussions, theoretical treatises, addresses, and brochures dealing with the great evolutionary problems, is distinctly anti-Darwinian in character. This major part of the public discussion of the status of evolution and its causes, its factors and mechanism, by working biologists and thinking natural philosophers, reveals a lack of belief in the effectiveness or capacity of the natural selection theory to serve as a sufficient causo-mechanical explanation of species-forming and evolution. Nor is this preponderance of anti-Darwinian expression in current biological literature to be wholly or even chiefly attributed to a dignified silence on the part of the believers in selection. Answers and defences have appeared and are appearing. But in practically all these defences two characteristics are to be noted, namely, a tendency to propose supporting hypotheses or theories, and a tendency to make certain

INTRODUCTORY: “DEATH-BED OF DARWINISM.” 5 distinct concessions to the beleaguering party. The fair truth is that the Darwinian selection theories, considered with regard to their claimed capacity to be an independently sufficient mechanical explanation of descent, stand to-day seriously discredited in the biological world. On the other hand, it is also fair truth to say that no replacing hypothesis or theory of species-forming has been offered by the opponents of selection which has met with any general or even considerable acceptance by naturalists. Mutations seem to be too few and far between ; for orthogenesis we can discover no satisfactory mechanism; and the same is true for the Lamarckian theories of modification by the cumulation,, through inheritance, of acquired or ontogenic characters.. Kurz und gut , we are immensely unsettled.

Now but little of this philosophic turmoil and wordy strife has found its way as yet into current American literature. Our bookshop windows offer no display, as in Germany, of volumes and pamphlets on the newer evolutionary study; our serious-minded quarterlies, if we have any, and our critical monthlies and weeklies contain no debates or discussions over “das Sterbelager des Darwinismus.” Our popular magazines keep to the safe and pleasant task of telling sweetly of the joys of making Nature’s acquaintance through field-glasses and the attuned ear. But just as certainly as the many material things “made in Germany” have found their way to us so will come soon the echoes and phrases of the present intellectual activity in evolutionary affairs, an activity bound to continue as long as the new lines of biological investigation continue their amazing output of new facts to serve as the bases for new critical attacks on the old notions and for the upbuilding of new hypotheses. If now the first of these echoes to come across the water to us prove to be, as wholly likely, those from the more violent and louder debaters, they may lead to an undue dismay and panic on our part. Things are really in no such desper-

DARWINISM TO-DAY.

ate way with Darwinism as the polemic vigour of the German and French anti-Darwinians leads them to suggest. Says one of them :5 “Darwinism now belongs to history, intemperate t^iat ot^er curiosity of our century, the

anti-Darwin- Hegelian philosophy ; both are variations on the theme : how one manages to lead a whole generation by the nose.” The same writer also speaks of “the softening of the brain of the Darwinians.” Another one,* in similarly relegating Darwinism to the past, takes much pleasure in explaining that “we [anti-Darwinians] are now standing by the death-bed of Darwinism, and making ready to send the friends of the patient a little money to insure a decent burial of the remains.” No less intemperate and indecent is Wolff’s T reference to the “episode of Darwinism” and his suggestion that our attitude toward Darwin should be “as if he had never existed.” Such absurdity of expression might pass unnoticed in the mouth of a violent non-scientific debater — let us say an indignant theologian of Darwin’s own days — but in the mouth of a biologist of recognised achievement, of thorough scientific training and unusually keen mind — for this expression came from just such a man — it can only be referred to as a deplorable example of those things that make the judicious to grieve. Such violence blunts or breaks one’s own weapons.

While I have said that the coming across the water of the more vigorous anti-Darwinian utterances might cause some dismay and panic in the ranks of the educated reader — really unnecessary panic, as I hope to point out — it will doubtless occur to some of my readers to say that this fear of panic is unwarranted. If the first phrases to come are as injudicious and intemperate, hence as unconvincing, as those just cited, the whole anti-Darwinian movement will be discredited and given no attention. Which, I hasten to reply, will be as much of a mistake as panic would be. There is something very seriously to be heeded in the

INTRODUCTORY: “DEATH-BED OF DARWINISM.” 7 chorus of criticism and protest, and wholly to stop one’s ears to these criticisms is to refuse enlightenment and to show prejudice. I have thought it, therefore, worth while to try to anticipate the coming of fragmentary this^book °f anc* disturbing extracts from the rapidly increasing mass of recent anti-Darwinian literature by presenting in this book a summary account not alone of these modern criticisms, but of the answers to them by the steadfast Darwinians, and of the concessions and supporting hypotheses which the supporters of both sides have been led to offer during the debates. I shall try to give a fair statement of the recent attacks on, and the defence and present scientific standing of, the familiar Darwinian theories, and to give also concise expositions, with some critical comment, of the more important new, or newly remodelled alternative and auxiliary theories of species-forming and descent, such as heterogenesis, orthogenesis, isolation, etc., and an estimate of their degree of acceptance by naturalists.

Appendix

1 Dennert, E., “Vom Sterbelager des Darwinismus,” Stuttgart, 1903. An intemperate and unconvincing but interesting brief against Dennert’s in- the Darwinian factors, i. e., the selection theories, in temperate attack evolution. Author fully accepts the theory of descent, on Darwinism. but jn no degree the Darwinian causal explanation of this descent. “Was ich in diesen Berichten nachzuweisen suche, ist die Tatsache, dass der Darwinismus nunmehr bald der Vergangenheit, der Geschichte angehort, dass wir an seinem Sterbelager stehen und dass auch seine Freunde sich eben anschicken, ihm wenigstens noch ein anstandiges Begrabnis zu sichern” (p. 4). The valuable thing about the paper is that it is largely given to a gathering together of the anti-Darwinian opinions and declarations of numerous, mostly well-known and reputably placed biologists. Some of these declarations are interpreted by Dr. Dennert in a way that would probably hardly be wholly acceptable to the declarers, but for the most part the anti-Darwinian beliefs of these biologists are unmistakably revealed by their own words. Among the biologists and biological philosophers thus agglomerated into the camp of

DARWINISM TO-DAY.

anti-Darwinism are Wigand, Haacke, von Sachs, Goette, Korschinsky, Haberlandt, Steinmann, Eimer, M. Wagner, von Kolliker, Nageli, Kerner, F. von Wagner, Fleischmann, O. Schultze, O. Hertwig, and others. This list includes reputable botanists, zoologists,, and palaeontologists.

2 For a recent account of such work, see Morgan, T. H., “Experimental Zoology,” 1907.

3 A. Fleischmann, professor of zoology in the University of Erlangen, is the only biologist of recognised position, of whom I am

An anti-evolu- aware, who publicly declares a disbelief in the theory tion university of descent. He seems to base his disbelief on the biologist. fact tjiat the phyletic (genealogic) series in numerous,

animal groups are as yet unexplained. See his book, “Die Descendenztheorie,” Leipzig, 1901. “Allein je mehr ich mich in die vermeintlichen Beweisgriinde derselben [the theory of descent] vertiefte und durch Spezialuntersuchungen positive Anhaltspunkte fiir die Stammesverwandtschaft der Tiere zu gewinnen suchte, um so klarer stellte sich mir die Erkenntniss heraus, dass jene Theorie eben doch mehr nur ein bestrickender, Ergebnisse und Aufklarung vortauschender Roman sei, als eine auf positiven Grundlagen aufgebaute Lehre.” (From the preface of this book).

* A curious attempt to formulate a scientific theory explaining the conditions as we know them in the world of life, to replace the