278 THE DESCENT OF MAN 



highly developed than those of the female, it may be that 

 the perfection of these is indispensable to the male for find- 

 ing the female; but in the vast majority of cases they serve 

 only to give one male an advantage over another, for with 

 sufficient time the less well-endowed males would succeed 

 in pairing with the females; and, judging from the structure 

 of the female, they would be in all other respects equally 

 well adapted for their ordinary habits of life. Since in such 

 cases the males have acquired their present structure not 

 from being better fitted to survive in the struggle for exist- 

 ence, but from having gained an advantage over other 

 males, and from having transmitted this advantage to their 

 male offspring alone, sexual selection must here have come 

 into action. It was the importance of this distinction which 

 led me to designate this form of selection as Sexual Selec- 

 tion. So again, if the chief service rendered to the male by 

 his prehensile organs is to prevent the escape of the female 

 before the arrival of other males, or when assaulted by 

 them, these organs will have been perfected through sexual 

 selection, that is by the advantage acquired by certain indi- 

 viduals over their rivals. But in most cases of this kind 

 it is impossible to distinguish between the effects of natural 

 and sexual selection. Whole chapters could be filled with 

 details on the differences between the sexes in their sensory, 

 locomotive, and prehensile organs. As^, however, these 

 structures are not more interesting than others adapted for 

 the ordinary purposes of life, I shall pass them over almost 

 entirely, giving only a few instances under each class. 



There are many other structures and instincts which 

 must have been developed through sexual selection — such 

 as the weapons of offence and the means of defence of the 

 males for fighting with and driving away their rivals — their 

 courage and pugnacity — their various ornaments — their con- 

 trivances for producing vocal or instrumental music — and 

 their glands for emitting odors, most of these latter struct- 

 ures serving only to allure or excite the female. It is clear 

 that these characters are the result of sexual and not ol 



