INTRODUCTION 25 



Special decorations or peculiarities in the external appearance 

 or appendages of the body are seen to have no significance 

 except in courtship, and it is not unreasonable to infer that 

 the individuals best endowed with beauty or melodiousness 

 of voice succeed oftenest, and impress their qualities on the 

 next generation more than their less fortunate fellows. As- 

 suming, then, that differences in the degree of development 

 of such peculiarities occur among the males in each genera- 

 tion, and that the best succeed in producing most offspring, 

 transmitting their advantages in various degrees to their 

 male progeny, the progressive evolution of such characters is 

 the necessary consequence. 



The theory, however, has not been universally accepted 

 by followers of Darwin. Mr. A. R. Wallace has been a 

 vigorous and consistent opponent of it. His objections are 

 clearly summarised and criticised by Romanes in his Darwin 

 and after Danvin, vol. i. 1892. One of them is, that the 

 supposed action of sexual selection would, if it occurred, be 

 wholly neutralised by the action of natural selection; for 

 unless the most highly-ornamented males preferred by the 

 females are also the most fitted for the other conditions of 

 life, they will be eliminated in the general struggle for 

 existence, and the chances must be small that the otherwise 

 best fitted males should be likewise the most highly-orna- 

 mented, unless there is a natural correlation between em- 

 bellishment and general perfection, which Mr. Wallace 

 maintains to be the case. Now this objection is not a very 

 powerful one, for it was obvious from the first that the 

 female could only exercise her choice among the individuals 

 which had survived in the struggle for existence, and 

 Darwin's theory simply maintains that after a male has 

 succeeded in getting a living and escaping his enemies, he 

 must compete for the possession of a mate before he can 

 leave progeny. 



