CHAPTER IV 



Secondary Sexual Characters and their Rela- 

 tion to Darwin's Theory of Sexual Selection 



In his "Origin of Species" Darwin has defined Sexual 

 Selection as depending "on a struggle between the 

 individuals of one sex, generally the males, for the 

 possession of the other sex. The result is not death 

 to the unsuccessful competitor, but few or no offspring. 

 Sexual selection is, therefore, less rigorous than natural 

 selection. Generally, the most vigorous males, those 

 which are best fitted for their places in nature, will 

 leave most progeny. But in many cases, victory 

 depends not so much on general vigor, as on having 

 special weapons, confined to the male sex. A hornless 

 stag or spurless cock would have a poor chance of leav- 

 ing numerous offspring. Sexual selection, by always 

 allowing the victor to breed, might surely give indomi- 

 table courage, length to the spur, and strength to the 

 wing to strike in the spurred leg, in nearly the same 

 manner as does the brutal cock-fighter by the careful 

 selection of his best cocks." 



Darwin continues: "Amongst birds, the contest 

 is often of a more peaceful character. All those who 

 have attended to the subject, believe that there is the 

 severest rivalry between the males of many species 

 to attract, by singing, the females. The rock-thrush 

 of Guiana, birds of paradise, and some others, con- 



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