204 EEY. J. T. GULICK ON DIVERGENT EVOLUTION 



In the case of Natural Selection, the separation it introduces 

 is between the living and the dead, between the successful and the 

 unsuccessful. In other words, Natural Selection is the exclusion 

 of all the forms that through lack of adaptation to the environ- 

 ment fail of leaving progeny, and therefore in the exclusive 

 generation of the forms that through better adaptation to the 

 environment are better able to propagate. Variation with tJie 

 Natural Selection of other than average forms may therefore ac- 

 count for the transformation of an ancient species into a series of 

 successive species the last of which may now exist in full force ; 

 hut without the aid of Regeneration it will hy no means account 

 for the divergent evolution of any one of these species into a family 

 of coexisting species. 



As I have just shown, Natural Selection is the exclusive genera- 

 tion of those better fitted to the environment ; and it tends to 

 the modification of species simply through the generation of the 

 better fitted forms, while they are prevented from crossing with 

 the less fitted, which fail of propagating through their lack of 

 fitness. Now from the very nature of this process, which results 

 from the success and failure of individuals in appropriating the 

 resources of the environment, it follows that it cannot be the 

 cause of separation between the successful competitors, and there- 

 fore any divergence of character that arises between the different 

 groups of the successful cannot be attributed to Natural Selec- 

 tion. Natural Selection explains the prevention of crossing 

 between the fitted and the unfitted, and shows how the succes- 

 sive generations of a species may gradually depart from the 

 original type, becoming in time a different species ; but it can- 

 not explain the divergences that arise ietween those that have, 

 hy the fact of successful propagation, proved their fitness. It 

 depends on superiority of adaptation to the environment, and 

 tends to produce increasing adaptation ; but divergent kinds of 

 adaptation are not necessary conditions for it, and it cannot he 

 the cause of increasing divergence hetween the incipient hinds that 

 otherwise arise. 



Divergent Evolution not explained by " the advantage 

 or divergence of character." 



Two sections of the 4th chapter of the ' Origin of Species ' 

 are given to the discussion of the " principle of benefit being 

 derived from divergence of character," which it is maintained 



