REPTILES AND AMPHIBIA 169 



to different modes of ordinary life, or to special habits con- 

 nected with sexual activity. 



The latter alternative is the true one. Notwithstanding 

 the curious mode of fertilisation, the generative act of the 

 male is not simply automatic, but is associated with sexual 

 excitement, and an eager pursuit and courtship of the female. 

 The mere presence and society of the female seems here to 

 afford the stimulation to the male organs which in mammals 

 and birds is supplied by the contact of her generative organs, 

 and the desire for the female produces the same sexual ex- 

 citement and leads to actions of the same kind as in those 

 classes. 



According to Darwin prehensile claws are developed on 

 the fore-legs of the males in some species during the breed- 

 ing season, which if correct indicates that the female is 

 seized and held by the male. In this case the mechanical 

 stimulation is obvious, and the special growth is limited to 

 the season of the year at which the stimulation is applied. 



In Molge palmata, the Webbed Newt, which is a British 

 species, the hind feet are webbed in the males during the 

 breeding season, when the animals live in the water. In 

 the rest of the year, when they live on land, the web almost 

 entirely disappears. Doubtless, as Darwin says, the structure 

 aids the male in his eager search and pursuit of the female, 

 but its origin is to be attributed to the effect of the resist- 

 ance of the water and the stretching of the toes in swimming. 

 If it was a variation not due to the mechanical strains 

 involved in swimming, why should it diminish after the 

 breeding season, when the animal leaves the water ? 



The well-developed membranous crest on back and tail in 

 our two common species of newt, Molge vulgaris and M. 

 cristata, seems much more difficult to explain. Like the 

 web of the hind feet in the palmata it diminishes very much 

 after the breeding season, and is almost entirely absent in 



