Recapitulation and Conclusion. 825 



It is plain that sexual selection must have the effect 

 which Dai'Avin attributes to it, but the fact that even in 

 choice breeds of domesticated animals which are mated 

 according to the wishes of the breeder^ and not according 

 to their own selection, the males are more modified than 

 the females, shows that behind the action of sexual selec- 

 tion some more profound law must exist. 



Darwin believes that this explanation is to be found in 

 the fact that the male usually has stronger passions than 

 the female, and is consequently more exposed to the action 

 of natural selection. He says that the perpetuation of 

 the race depends upon the existence of the sexual passion, 

 and that, since the male must in most cases seek the 

 female, the most eager males have left the greatest num- 

 ber of offspring, and have thus become selected. 



When we bear in mind the fact that the parental 

 instinct is fully as important to the race as the sexual 

 instinct, and that this is usually most developed in the 

 female, we see that the failure of the female to undergo 

 modification for the good of the species as frequently as 

 the male cannot be explained without the recognition of 

 some more general law. The singular history of second- 

 ary sexual characters receives a ready explanation by the 

 law of heredity, for this law leads us to look to the cells 

 of the male body for the origin of most of the variations 

 through which the species has attained to its present 

 organization. 



Since gemmules which originate in a male body are 

 more likely to be transmitted than those formed in a 

 female body, and since gemmules are most likely to be 

 formed in the sex in which an organ is of most functional 

 importance, and therefore most subject to disturbing 

 influences, we can readily see why a part which is im- 



