34 



SEXUAL SELECTION. 



[Part IL 



differ so mucli in appearance from the two great prolon- 

 gations of the skull in C. bifurcus^ we can hardly doubt 

 that they serve the same general purpose in the economy 

 of these two animals. The first conjecture which will 

 occur to every one is that they are used by the males for 

 fighting together; but Dr. GUnther, to whom I am in- 

 debted for the foregoing details, does not believe that 

 such peaceable creatures would ever become pugnacious. 



Hence we are 

 driven to infer 

 tliat these almost 

 monstrous devia- 

 tions of structure 

 serve as mascu- 

 line ornaments. 



With many 

 kinds of lizards, 

 the sexes differ 

 slightly in color, 

 the tints and 

 stripes of the 

 males being 



Fia. 36.— Chamaelcon Owenii. Upper figure, male ; brighter and 

 lower figure, female. '^ -,• . 



more distinctly 

 defined than in the females. This, for instance, is 

 the case with the previously-mentioned Cophotis and 

 "with the Acanthodactylus cajyensis of South Africa. 

 In a Cordylus of the latter coimtry, the male is either 

 much redder or greener than the female. In the Indian 

 Calotes nigrilahris there is a greater difference in color 

 between the sexes ; the lips also of the male are black, 

 while those of the female are green. In our common little 

 vivij>arous lizard [Zootoca tu'vipara), " the umlcr side of 

 the body and base of the tail in the male are bright 

 orange, spotted with black ; in the female these parts are 



