130 HEREDITY AND SEX 



In the Eastern States there is a butterfly, Colias 

 philodice, in which two types of female exist (Fig. 66). 

 Gerould has studied the mode of inheritance of these 

 two types and finds that they conform to a scheme in 

 which the two females differ by a single factor. The evi- 

 dence is strongly in favor of the view that one of these 

 forms has arisen as a mutation. There is no need to 

 suppose that sexual selection has had anything to do 

 with its origin, and no evidence that it owes its exist- 

 ence to mimicry of any other species. 



Finally, I should like to speak of a case that has come 

 under my own observation. One of the mutants that 

 appeared in a culture of drosophila had a new eye 

 color that was called eosin. In the female the eye is 

 much deeper in color than in the male. The race main- 

 tains itself as a bicolor type without any selection. 



CONCLUSIONS 



In conclusion let me try to bring together the main 

 considerations that seem to me to throw serious doubts 

 on Darwin's theory of sexual selection. 



First. Its fundamental assumption that the evolution 

 of these characters has come about through the ''will," 

 ''choice," or selection of the female is questionable, 

 because of want of evidence to show that the females 

 make their choice of mates on this basis. There is also 

 some positive evidence to show that other conditions 

 than selection of the more ornamented individual 

 (because he is the more ornamental) are responsible 

 for the mating. 



Second. We have come to have a different concep- 

 tion of what selection can do than the sliding scale 



