28 Gulick — Divergent Evolution and the Darwinian Theory. 



appeared to me a great difficulty ; but it arises in chief part 

 from the deeply seated error of considering the physical con- 

 ditions of a country as the most important ; whereas it cannot 

 be disputed that the nature of the other species with which 

 each has to compete, is at least as important, and generally a 

 far more important element of success. Now if we look to 

 the species which inhabit the Galapagos Archipelago, and are 

 likewise found in other parts of the world, we find that they 

 differ considerably in the several islands." — [Origin of Species, 

 near the middle of the second chapter on Geographical Distri- 

 bution.]* 



The implication in both these passages is that if the repre- 

 sentatives of the same species are surrounded by the same 

 organic forms as well as by the same physical conditions in 

 isolated countries, they will not undergo divergent modifica- 

 tion. This is in complete accord with the third paragraph 

 quoted near the beginning of this paper from the 4th chapter 

 of the " Origin of Species." 



Divergent Forms of Sexual Selection. 



In the passages last quoted there is no mention of any 

 exception to the principle that difference in external condi- 

 tions is necessary to divergent evolution. No suggestion is 

 given that through the action of sexual selection divergent 

 species may be produced that are not at all dependent on 

 differences in the environments, still there can be no doubt 

 that this was Darwin's view. Though he does not directly 

 discuss this problem in any passage I have been able to dis- 

 cover, he clearly expresses the opinion that the differences 

 between the different races of man, and between man and the 

 lower animals, are in no small degree due to sexual selection, 

 and he never speaks of difference in sexual selection as depend- 

 ing on difference in the environment, though, at the close of 

 the twentieth chapter of " The Descent of Man," he speaks of 

 sexual selection in man as having probably " exaggerated " the 

 " characteristic qualities " " which are of no service to " the 

 tribes and races that possess them. The differences, however, 

 in the races of man are attributed to sexual selection, not 

 because of any lack of difference in their environments, but 

 because the characters in which they differ do not seem to 

 him to be related to the environment. The color of the skin, 

 hair, and eyes, and the different forms of the head and face do 

 not seem to be adapted to different conditions in the environ- 

 ment,' while they are undoubtedly occasions of attraction or 

 aversion for those seeking partners. He has not, however, 



*See ed. 6, p. 355. 



