2 1 The Descent of Man. Part II 



like a rasp, and with this they coil round and permanently hold 

 the females. 4 



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

 the male has the sensory or locomotive organs more highly 

 developed 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 

 designate 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 

 acquired 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 

 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 contrivances for pro- 



4 M. Perrier advances this case claspers of certain male animals 

 ('Revue Scientifique,' Feb. 1, 1873, could not have been developed 

 p. 865) as one fatal to the belief in through the choice of the female ! 

 sexual selection, inasmuch as he Had 1 not met with this remark, I' 

 supposes that I attribute all the should not have thought it possible 

 differences between the sexes to for any one to have read this chapter 

 sexual selection. This distinguished and to have imagined that I main- 

 naturalist, therefore, like so manj tain that the choice of the female 

 other Frenchmen, has not taken the had anything to do with the develop- 

 trouble to understand even the first ment of the prehensile organs in the 

 principlss of sexual selection. An male. 

 English nationalist insists that the 



