opinions on Isolation. 103 



standard of perfection, and all try to procure and breed from the 

 best animals, improvement surely but slowly follows from this 

 unconscious process of selection, notwithstanding that there is no 

 separation of selected individuals. Thus it will be under nature \ 



Here we have what may perhaps be regarded as a 

 glimmering of the distinction between monotypic and 

 polytypic evolution. But that it is only a glimmering 

 is proved by the immediately ensuing sentences, which 

 apply this analogy of unconscious selection not to the 

 case of monotypic, but to that of polytypic evolution. 

 So likewise, in the succeeding discussion on "'divergence 

 of character," the analogy is again resorted to for the 

 purpose of showing how polytypic evolution may occur 

 in nature. 



Thus far, then, it may be said that we have scarcely 

 so much as a glimmering of the distinction between 

 monotypic and polytypic evolution ; and as the same 

 discussion (with but a few verbal alterations) runs 

 through all the editions of the Origin, it may well be 

 asked why I should have alluded to such passages in 

 the present connexion. Well, I have done so because 

 it is apparent that, during the last years of his life, the 

 distinction between selection as " methodical " and 

 " unconscious " enabled Darwin much more clearly to 

 perceive that between evolution as monotypic and 

 polytypic. Thus in iS68 he wrote to Moritz Wagner 

 (who, as we shall presently see, entirely failed to 

 distinguish between monotypic and polytypic evolu- 

 tion), expressing his belief — 



That in many large areas all the individuals of the same 

 species have been slowly modified, in the same manner, for 

 instance, as the English racehorse has been improved, that is, 



' Origin of Species, p. 80. 6th eci. (1S72). 



