SEXUAL SELECTION. 237 



organs of sense and locomotion, but if these organs are 

 necessary for tho other purposes of life, as is generally the 

 case, they will have been developed through natural selec- 

 tion. When the male has found the female he sometimes 

 absolutely requires prehensile organs to hold her; thus Dr. 

 Wallace informs me that the males of certain moths cannot 

 unite with the females if their tarsi or feet are broken. 

 The males of many oceanic crustaceans, when adult, have 

 their legs and antennae modified in an extraordinary 

 manner for the prehension of the female; hence we may 

 suspect that it is because these animals are washed about 

 by the waves of the open sea that they require these organs 

 in order to propagate their kind, and, if so, their develop- 

 ment has been the result of ordinary or natural selection. 

 Some animals extremely low in the scale have been modified 

 for this same purpose; thus the males of certain parasitic 

 worms, when fully grown, have the lower surface of the 

 terminal part of their bodies roughened like a rasp, and 

 with this they coil round and permanently hold the 

 females.* 



When the two sexes follow exactly the same habits of 

 life, and the male has the censory 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 suc- 

 ceed 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 struct- 

 ure not from being better fitted to survive in the struggle 



*M. Perrier advances this case ("Revue Scientifique," Feb. 1, 

 1873, p. 865) as one fatal to the belief in sexual selection, inasmuch 

 as he supposes that I attribute all the differences between the sexes 

 to sexual selection. This distinguished naturalist, therefore, 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 devel- 

 oped through the choice of the 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 inaintain that the 

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

 prehensile organs in the male. 



