Chap. VIII. SEXUAL SELECTION. 299 



of and accumulated through sexual selection in rela- 

 tion to the reproduction of the species ; therefore it 

 appears, at first sight, an unaccountable fact that simi- 

 lar variations have not frequently been accumulated 

 through natural selection, in relation to ordinary habits 

 of life. If this had occurred, the two sexes would fre- 

 quently have been differently modified, for the sake, 

 for instance, of capturing prey or of escaping from 

 clanger. We have already seen and shall hereafter 

 meet with other instances of differences of this kind 

 between the two sexes, especially with the lower ani- 

 mals; but they are rare in the higher classes. We 

 should, however, bear in mind that the sexes in the 

 higher classes generally follow the same habits of life ; 

 and supposing that the males alone varied in a manner 

 favouring their power of gaining subsistence, &c, and 

 transmitted such variations to their male offspring 

 alone, these would acquire an organization superior to 

 that of the females ; but it is probable that the females, 

 from having the same general constitution and from 

 being exposed to the same conditions, would sooner or 

 later vary in the same manner ; and as soon as this 

 occurred, the variations would be equally preserved 

 through natural selection in the two sexes, which would 

 thus ultimately become like each other. The case is 

 widely different with variations accumulated through 

 sexual selection ; for the habits of the two sexes in 

 relation to the reproductive functions are not the same, 

 and sexually-transmitted modifications serviceable to 

 the one sex would in it be preserved, whilst similar 

 modifications would often be quite useless to the other 

 sex, and consequently would in this latter soon be lost. 



In the following chapters, I shall treat of the 

 secondary sexual characters in animals of all classes, 



