172 Evolution and Adaptation 



" But it is difficult to understand why the males of species, 

 of which the progenitors were primordially free, should in- 

 variably have acquired the habit of approaching the females, 

 instead of being approached by them. But in all cases, in 

 order that the males should seek efficiently, it would be 

 necessary that they should be endowed with strong passions ; 

 and the acquirement of such passions would naturally follow 

 from the more eager leaving a larger number of offspring 

 than the less eager." 



Thus we are led to the rather complex conclusion, that 

 the more eager males will leave more descendants, and those 

 that are better endowed with ornaments will be the ones 

 selected. But unless it can be shown that there is some 

 connection between greater eagerness and better ornamenta- 

 tion, it might often occur that the less ornamented were the 

 more eager individuals, in which case there would be an 

 apparent conflict between the two acquirements. 



After giving some cases of the greater variability of the 

 males, in respect to characters that are not connected with 

 sexual selection, and presumably not the result of any kind 

 of selection, Darwin concludes : " Through the action of 

 sexual and natural selection male animals have been rendered 

 in very many instances widely different from their females ; 

 but independently of selection the two sexes, from differing 

 constitutionally, tend to vary in a somewhat different man- 

 ner. The female has to expend much organic matter in the 

 formation of her ova, whereas the male expends much force 

 in fierce contests with his rivals, in wandering about in 

 search of the female, in exerting his voice, pouring out 

 odoriferous secretions, etc. : and this expenditure is gen- 

 erally concentrated within a short period. The great vigor 

 of the male during the season of love seems often to in- 

 tensify his colors, independently of any marked difference 

 from the female. In mankind, and even as low down in the 

 organic scale as in the Lepidoptera, the temperature of the 



