258 ODD HOURS WITH NATURE 



by disease or direct injury, and the appearance of 

 the secondary male characters after the ruin of 

 female characters has some important implications. 

 There is no subject in natural history on which 

 greater battles of theory have been fought than 

 the development of the ornamental and other 

 secondary sex characters of the males of dimorphic 

 species. Darwin explains them by his famous 

 theory of sexual selection, which, in the case of 

 birds, attributes to the female an aesthetic sense 

 which the male must satisfy. By the constant 

 selection of the males best capable of gratifying 

 this sense, the gorgeous tails of the peacock and 

 argus pheasant have been built up. In this theory 

 the characters are developed in the male alone, 

 for in him alone is there a call for them. Another 

 theory which has somewhat more favour to-day 

 assumes that the male of, say, peacock or pheasant 

 represents the normal race development which 

 would have resulted in equally beautiful members 

 of both sexes but for some inhibitory force 

 operating on the female alone. The inhibitory 

 power is a variation which natural selection has 

 fixed in the females by eliminating those that did 

 not possess it conspicuous females falling easy 

 victims to enemies when tied to the nest by the 

 duty of incubation. In support of this explanation 

 it is possible to cite many examples, all to the 

 purpose that the birds in which high beauty is 

 confined to the male are open nesters ; whereas 

 in the case of hidden nesters the kingfisher is a 

 case in point both male and female have evolved 

 in beauty equal in extent and kind. 



