Chap. VIII. SEXUAL SELECTION. 257 



of life, and the male has more highly developed sense 

 or locomotive organs than the female, it may be that 

 these in their perfected state are indispensable to the 

 male for finding the female ; but in the vast majority 

 of cases, they serve only to give one male an advan- 

 tage over another, for the less well-endowed males, 

 if time were allowed them, would succeed in pair- 

 ing with the females ; and thev would in all other 

 respects, judging from the structure of the female, be 

 equally well adapted for their ordinary habits of life. 

 In such cases sexual selection must have come into 

 action, for the males have acquired their present struc- 

 ture, not from being better fitted to survive in the 

 struggle for existence, but from having gained an ad- 

 vantage over other males, and from having transmitted 

 this advantage to their male offspring alone. It was the 

 importance of this distinction which led me to designate 

 this form of selection as sexual selection. So again, 

 if the chief service rendered to the male by his pre- 

 hensile 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 males over their rivals. But in most cases it 

 is scarcely possible to distinguish between the effects 

 of natural and sexual selection. Whole chapters could 

 easily be filled with details on the differences between 

 the sexes in their sensorv, locomotive, and prehensile 

 organs. As, however, these structures are not more 

 interesting than others adapted for the ordinary pur- 

 poses of life, I shall almost pass them over, 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 



VOL. L s 



