214 Heredity. 



sable to the male for finding the female; but in the vast 

 majority of cases they serve only to give one male an ad- 

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

 if time were allowed them, would succeed in pairing with 

 the females; and they would in all other respects, judg- 

 ing 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 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. It was the importance of this 

 distinction which led me to designate this form of selec- 

 tion as sexual selection. So, again, if the chief service 

 rendered to the male by his prehensile organs is to pre- 

 vent the escape of the female before the arrival of otlier 

 males, or when assaulted by them, these organs will 

 have been fortified 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. . . . 

 There are many structures and instincts which must 

 have been developed through sexual selection, such as 

 the weapons of offence and the means of defence pos- 

 'sessed by the males for fighting with and driving away 

 their^ivals — their courage and pugnacity — their orna- 

 ments of many kinds — their organs for producing vocal 

 or instrumental music, and their glands for emitting 

 odors; most of these latter structures serving only to al- 

 lure or excite the females. That these characters are 

 the result of sexual and not of ordinary selection is clear, 

 as unarmed, unornamented, or unattractive males would 

 succeed equally well in the battle for life, and in leav- 



