26 Dai'zvin, and after Darwin. 



alone, can never induce polytypic evolution, but 

 only monotypic. 



Now I regret to say that here, for the first and 

 onl}- time throughout the whole coarse of the 

 present treatise, I find myself in seeming opposition 

 to the views of Darwin. For it was the decidedly 

 expressed opinion of Darwin that natural selection 

 is competent to effect polytypic, or divergent, evo- 

 lution. Nevertheless, I believe that the opposition 

 is to a large extent only apparent, or due merely to 

 the fact that Darwin did not explicitly state certain 

 considerations which throughout his discussion on 

 "divergence of character" are seemingly implied. 

 But, be this as it may, I have not even appeared 

 to desert his leadership on a matter of such high im- 

 portance without having duly considered the question 

 in all its bearings, and to the utmost limit of my 

 ability. Moreover, about two years after the publica- 

 tion of my first paper ^ upon the subject, Mr. Gulick 

 followed, at somewhat greater length, in the same line 

 of dissent. Like all the rest of his work, this is so 

 severely logical in statement, as well as profoundly 

 thought out in substance, that I do not see how it 

 is possible for any one to read impartially what he 

 has written, and then continue to hold that natural 

 selection, if unassisted by any other form of isola- 

 tion, can possibly effect divergence of character — 

 or polytypic as distinguished from monotypic evo- 

 lution ^. 



I may here quote from Mr. Gulick's paper three 

 propositions, serving to state three large and general 



■ Zeol. Journal Lin. Soc, vol. xix. pp. 337-411, 

 ' Ibid., vol. XX. pp. 202-212. 



