200 ORGANIC EVOLUTION CONSIDERED 



identical in structure with those of a bull, goat, or 

 other sheath-horned ruminant." He thinks that 

 "these almost monstrous deviations of structure 

 serve as masculine ornaments," and that they have 

 been developed by sexual selection. 



In this instance we meet with the usual difficulties : 

 First, the absence of evidence to show that female 

 reptiles of this species or of auy other species exer- 

 cise any such choice, and second, that the exercise of 

 choice implies the development to a considerable 

 extent of the organ concerning which the choice is 

 exercised. 



It cannot be presumed that in the great multitude 

 of instances in which Mr. Darwin claims that sexual 

 selection has been efficient it has acted on the 

 merest rudiments, and yet this assumption lies at the 

 foundation of his theory. I regard this as a fatal 

 objection to the theory of sexual selection. 



Among birds sometimes both sexes are colored 

 alike, but in many cases the males are more highly 

 and in exceptional cases less highly ornamented than 

 the females. Mr. Darwin admits that, as a rule, it 

 cannot be useful to birds to be highly ornamented. 

 The greatly developed and gaudy feathers, such as 

 those of many male pheasants, render them more con- 

 spicuous to their enemies, and, consequently, their 

 long tails and beautiful colors could not have been pro- 

 duced by natural selection. He refers their evolution to 

 sexual selection. He claims, however, that the highly 

 colored males are, as a rule, given to combat with 

 each other for the females, so that combat instead of 

 beauty would be the principal factor in these cases. 

 There are no facts going to show that the most beau- 

 tiful birds would, on the average, be most successful 

 in combat, and unless this were true I do not see how 

 sexual selection could increase the beauty of the 



