206 THE DESCENT OP MAN. 



When the two sexes follow exactly the same habits of life, and 

 the male has the sensory or locomotive organs more highly de- 

 veloped than those of the female, it may be that the perfection of 

 these is indispensable to the male for finding 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 existence, 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 desig- 

 nate this form of selection as Sexual Selection. 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 ac- 

 quired by certain individuals 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 struc- 

 tures are not more interesting than others adapted for the or- 

 dinary 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 offense and the means of defense of the males for fighting 

 with and driving away their rivals — their courage and pugnacity 

 — their various ornaments— their contrivances for producing vo- 

 cal or instrumental music — and their glands for emitting odors, 

 most of these latter structures serving only to allure or excite 

 the female. It is clear that these characters are the result of 

 sexual and not of ordinary selection, since unarmed, unorna- 

 mented, or unattractive males would succeed equally well in the 



sexual selection. This distinguished naturalist, tlierefore, like so 

 many other Frenchmen, has not taken the trouble to understand even 

 the first principles of sexual selection. An English naturalist insists 

 that the claspers of certain male animals could not have been de- 

 veloped through the choice of fhe female! Had I not met with this 

 remark, I should not have thought it possible for any one to have 

 read this chapter and to have imagined that I maintain that the 

 choice of the female had anything to do with the development of the 

 prehensile ors:ans in the male. 



