I04 Darwin, and after Darwin. 



by the continued selection of the fleetest individuals, without 

 any separation. But I admit that by this process two or 

 more new species could hardly be formed within the same limited 

 area'. 



Again, in 1876 he wrote another letter to Wagner, 

 in which the following passage occurs : — 



I believe that all the individuals of a species can be slowly 

 modified within the same district, in nearly the same manner as 

 man effects by what 1 have called the process of unconscious 

 selection. I do not believe that one species will give birth to 

 two or more new species as long as they are mingled together 

 within the same district*. 



Two years later he wrote to Professor Semper : — 



There are two different classes of cases, it appears to me, 

 viz. those in which species becomes slowly modified in the 

 same country, and those cases in which a species splits into two, 

 or three, or more new species ; and, in the latter case, I should 

 think nearly perfect separation would greatly aid in their 

 "specification," to coin a new word*. 



Now, these passages show a very much clearer 

 perception of the all-important distinction between 

 monotypic and polytypic evolution than any which 

 occur in the Origin of Species ; and they likewise 

 show that he was led to this perception through what 

 he supposed to be a somewhat analogous distinction 

 between " unconscious " and " methodical " selection 

 by man. The analogy, I need hardly say, is radically 

 unsound ; and it is a curious result of its unsoundness 

 that, whereas in the Origin of Species it is adduced 

 to illustrate the process of polytypic evolution, as 

 previously remarked, in the letters above quoted we 



^ Life and Letters, voL iii. p. 158. 

 ^ Ibid. p. 159. ^ Ibid. p. i6o. 



