SEXUAL SELECTION. 



211 



female selection. The utmost that can be claimed for 

 the latter is, that a small fraction of the least ornamented 

 do not obtain mates, while a few of the most orna- 

 mented may leave more than the average number of 

 offspring. Unless, therefore, there is the strictest cor- 

 relation between ornament and general perfection, the 

 more brightly coloured or ornamented varieties can 

 obtain no permanent advantage ; and if there is (as I 

 maintain) such a correlation, then the sexual selection 

 of colour or ornament, for which there is little or no 

 evidence, becomes needless, because natural selection 

 which is an admitted vera causa, will itself produce all 

 the results. 



In the case of butterflies the argument becomes even 

 stronger, because the fertility is so much greater than 

 in birds, and the weeding-out of the unfit takes place, to 

 a great extent, in the egg and larva state. Unless the 

 eggs and larvae which escaped to produce the next 

 generation were those which would produce the more 

 highly- coloured butterflies, it is difficult to perceive how 

 the slight preponderance of colour sometimes selected by 

 the females, should not be wholly neutralized by the ex- 

 tremely rigid selection for other qualities to which the 

 offspring in every stage are exposed. The only way in 

 which we can account for the observed facts is, by the 

 supposition that colour and ornament are strictly corre- 

 lated with health, vigour, and general fitness to survive. 

 We have shown that there is reason to believe that this 

 is the case, and if so, conscious sexual selection becomes 

 as unnecessary as it would certainly be ineffective. 



Greater Brilliancy of some Female Birds. — There is 

 one other very curious case of sexual colouring among 



p 2 



