The Evidence from Sexual Characters. 217 



which must pair with the less vigorous and less attract- 

 ive males. So it will be if the more vigorous males se- 

 lect the more attractive and, at the same time, healthy 

 and vigorous females; and this will especially hold good 

 if the male defends the female and aids in providing food 

 for the young. The advantage thus gained by the more 

 vigorous pairs in rearing a larger number of offspring 

 has apparently sufficed to render sexual selection effi- 

 cient." 



The Study of Domesticated Races shows that this 

 Explanation does not go to the Root of the Matter. 



' This long extract will, I hope, fully explain to those 

 readers who are not familiar with Darwin's essay, the 

 nature of sexual selection. It will be seen that he at- 

 tributes the greater modification of the males as com- 

 pared with the females, in most of the groups of animals 

 where the sexes differ, to the fact that the males have 

 struggled with each other for the possession of the 

 females, or have been chosen by the females. This pro- 

 cess, long continued, is believed to have resulted in the 

 perpetuation of the strongest, best armed, or most at- 

 tractive males. 



I fully acknowledge the great potency of sexual selec- 

 tion, and believe with Darwin that it must act in essen- 

 tially the manner described by him, but I do not believe 

 that it goes to the root of the matter. 



Fortunately there is a simple experimental test which 

 is easily tried and gives a satisfactory solution of the 

 question whether the phenomena do or do not depend 

 upon something more fundamental than the exposure of 

 the male to the action of selection. 



If we take animals in which the sexes differ but little, 

 and prevent them from following their own inclinations, 



