484 



NA TURE 



[June 24, 1909 



discovery of the principle of natural selection, but is 

 due lo lh< circumstance that that work brought con- 

 viction to naturalists as well as to the educated public 

 of the truth of evolution as a principle. It unquestion- 

 ably did so, but since the assertion has been made 

 ihat without LaniarcUism the " Origin " would have 

 been a dillcrent work, it may be permissible to raise 

 (he question whether, without n.itural selection, the 

 mere marshalling of the facts of evolution — even by 

 the master mind of Darwin — would have done more 

 towards establishing that principle than did the 

 writings of the pre-Darwinian evolutionists or the 

 powerful advocacy of Herbert Spencer before the 

 publication of Darwin's work. .At any rate, the dis- 

 covery of natural selection was the cause of the 

 publication of the " Origin," and the success of that 

 book is attributable to the theory — the working 

 mechanism of species formation which, rightly or 

 wrongly, it proclaimed. 



jNot the least v.iluable feature of this volume of essays 

 is that, by bringing together the views of the different 

 and often ant.-igonistic writers, it enables the ordinary 

 reader to gel a clear notion of the various lines of 

 divergence from Darwin's original position. The 

 representatives of the modern school of " genetics," 

 for ex.uiiple, base their homage on the fact that he 

 introduced scientific method into the study of varia- 

 tion and heredity : — 



" Evolution is a process of variation and heredity. 

 7he older writers, though they had some vague idea 

 that it must be so, did not study variation and 

 heredity. Darwin did, and so begat not a theorv, but 

 a science " (Bateson, p. 88). 



Perfectly true so far as it goes; but his study of 

 variation and heredity was prompted from beginning 

 to end by his desire to find out how the raw materials 

 were supplied by n.iture for the action of natural 

 selection (see the introduction to " Variation of 

 Animals and Plants," passim). Also it is now a 

 matter of history that Darwin's work in this very line 

 of study did beget a theory— the " provisional hypo- 

 thesis of Pangenesis," of which Stnisburger says 

 (p. in):— 



"We can however .-iffirm that Charles Darwin's 

 idea that invisible gemmules are the carriers of here- 

 ditary characters .-ind th.it they multiply bv division 

 has been removed from the jxisition of a provisional 

 hypothesis lo that of a well-founded theory. It is 

 supported by histology, and the results of experimental 

 work in heredity, which are now assuming extra- 

 ordinary prominence, are in close agreement with it." 



There can be no reasonable doubt in the minds of 

 those who are f.imiliar with Darwin's books that his 

 study of variation and heredity centred round his 

 main theon,- of natural selection, and the first question 

 that the " educated la\man " may well ask in this 

 connection is. How far has our knowledge been 

 extended since Darwin's time? It does not appear 

 from the present body of evidence that we h.ive got 

 very much beyond Darwin with respect lo the causes 

 of variation in nature. Some ingenious hypotheses 

 have been suggested, and varieties have been classified 

 and put into named categories, but that is all. With 

 NO. 2069, VOL. 80] 



respect to heredity it is generally conceded that when 

 certain varieties appear the laws which determine their 

 transmission are nt>\v, thanks to the experiments of 

 Mendel and those who are continuing his work, being 

 definitely established. This is undoubtedly a most im- 

 portant line of investigation, and evolutionists will 

 anxiously await further developments. In the mean- 

 time, however, it would appear that at the halting 

 period marked by this present volume, the experiments 

 on cross-breeding have not vet contributed anything 

 constructively to the main problem which Darwin set 

 out to solve, since we have it on the authority of the 

 leader in this class of work that " the time is not ripe 

 for the discussion of the origin of species." 



With respect lo another divergence since Darwin's 

 time, viz. the mutation theory of de Vries, readers 

 must be referred to the author's own account (Essay 

 iv., p. 6<)). Want of space forbids an analysis of this 

 later departure in the way of " saltatory evolution," 

 only it must be noted that this kind of variation was 

 considered by Darwin over and over again, and 

 always with the conclusion that it played no important 

 part in the formation of species in nature. It will be 

 noted also that de Vries still subordinates his 

 " mutations " to the action of natural selection, and to 

 this extent is "a follower of Darwin. .Mthough the 

 bearing of this aspect of variation u|xin Darwin's 

 theory has been discussed by many able writers, it 

 may be useful at this period to direct attention to the 

 fact that it is unhesitatingly rejected by Haeckel as 

 giving no explanation of adaptations and as having 

 " no causal value " (p. 141). Here is what Darwin 

 wrote on this point in the last edition of the 

 " Origin " : — 



" Mr. Mivnrt is further inclined to believe, and 

 some naturalists agree with him, that new species 

 manifest themselves ' with suddenness and by modifi- 

 cations appearing at once.' . . . This conclusion, 

 which implies great breaks or discontinuity in the 

 scries, appears to me improbable in the highest 

 degree " (p. 201). 



" Although very many species have almost certainly 

 been produced by sleps not greater than those separat- 

 ing fine varieties; yet it may be mainl.-iined that some 

 have been developed in a different and abrupt manner. 

 Such an admission, however, ought not to be made 

 without strong evidence being assigned " (p. 203). 



Whether the evidence offered on behalf of this 

 divergence from the " Origin " is sufficiently strong 

 to warrant its adoption is still an open question (see 

 Poulton's "Essays on Evolution," introduction, 

 p. xiv). It is true that the author of modern 

 " niutationism " is inclined to believe that Darwin 

 recognised two kinds of variation, ordinary fluctua- 

 tions and those which " happen to arise " (" Origin," 

 sixth edition, p. itx)), but those who have really 

 mastered Darwin's meaning will agree with Prof. 

 Seward's and Mr. Kr.mcis Darwin's contention (p. 71, 

 footnote, of present work) th.at this interpretation of 

 the passage in the " Origin " is incorrect. This, by 

 the way, is the only " editorial " comment to be found 

 in the volume under consideration. 



Now, if we ask ourselves what has been the net 

 result of the publication of the " Origin of Species" 



