56 ORGANIC EVOLUTION 



secures the perpetuation of those characters in the male which 

 make him attractive to the female, irrespective of any advan- 

 tage or disadvantage in the struggle for existence. Those 

 males which are attractive will, because of their attractiveness, 

 get mates and have offspring, while many of the less attrac- 

 tive males will fail to find mates. In time, then, through the 

 action of this preference on the part of the females, there 

 will be developed a race whose males show the characters 

 which are attractive to the females. The results of sexual 

 selection are different from those produced by natural selec- 

 tion, and may often be opposed to the latter. For example, 

 it is of advantage to most birds to be inconspicuously col- 

 ored, so that they may more readily escape their enemies. 

 Natural selection, therefore, will tend to produce protec- 

 tively colored forms. Sexual selection, on the other hand, 

 in the case of many species, tends to produce brilliantly 

 colored males. The two tendencies are thus often opposed 

 to one another, sometimes one, sometimes the other, pre- 

 dominating. 



Important objections have been urged against the theory 

 of sexual selection. Many species of animals which show 

 bright colors or ornaments in the male that are not found in 

 the female are forms in which we have observed no court- 

 ing habits by which these adornments are displayed before 

 the female ; and many of these are forms in which we would 

 not expect to find the females exercising choice on the basis 

 of the ornamentation of the male. Note, for example, the 

 beetles (Plates 29 and 30, and Fig. 7) and certain lowly Crus- 

 tacea (Fig. 8, A). If the peculiar adornment of the males 

 in these species is due to something other than sexual selec- 



