SEXUAL SELECTION 107 



excision of the sexual organs or of certain of their 

 parts brings about the disappearance of those charac- 

 ters. We only need to recall the experiments of 

 Bouin and Ancel on the interstitial gland of the testi- 

 cles of mammals, which prove that the secretion of 

 that gland is responsible for the secondary sexual 

 characters and for the sexual instinct itself. It has 

 also been demonstrated experimentally that chemical 

 changes arise in the tissues of certain animals, fishes 

 for example, at breeding time. 



Although the theory of sexual selection is to be dis- 

 carded in its entirety, we must not exaggerate the 

 bearing its passing away will have upon the Darwin- 

 ian theory in general. Certain naturalists see in it 

 such an important corollary of the theory of natural 

 selection, that if the theory of sexual selection was 

 abandoned, they would consider the theory of natural 

 selection as doomed. We refuse to share this ex- 

 treme view. 



There were facts which Darwin could not explain 

 without calling into service a special theory. This 

 special theory may be replaced by another special the- 

 ory but the value of the theory of natural selection, as 

 far as it supplies an explanation for a large number 

 of facts, remains unimpaired. The inadequacy, now 

 fully recognised, of the theory of sexual selection 

 should not be used as a weapon against the theory of 

 natural selection. 



