33 



SEXUAL SELECTION. 



[Part II. 



rived at maturity, at which age the middle appendage is 

 sometimes twice as long as the head. Most of the species 

 likewise have a low crest running along the neck ; and this 

 is much more developed in the full-grown males than in 

 the females or young males. 50 



There are other and much more remarkable differences 

 between the sexes of certain lizards. The male of Cerato- 

 phora aspera bears on the extremity of his snout an 

 appendage half as long as the head. It is cylindrical, 

 covered with scales, flexible, and apparently capable of 

 erection : in the female it is quite rudimental. In a second 

 species of the same genus a teraninal scale forms a minute 

 horn on the summit of the flexible appendage ; and in a 

 third species (<7. Stoddartii, Fig. 34), the whole append- 

 age is converted into a horn, 

 which is usually of a white color, 

 but assumes a purplish tint when 

 the anilnal is excited. In the 

 adult male of this latter species 

 the horn is half an inch in length, 

 but is of quite minute size in the 

 female and in the young. These 

 appendages, as Dr. Giinther has 

 remarked to me, may be com- 

 pared with the combs of galli- 

 naceous birds, and apparently 

 serve as ornaments. 



In the genus Chameleon 

 we come to the climax of dif- 

 ference between the sexes. The upper part of the skull 

 of the male C. bifurcus (Fig. 35), an inhabitant of Mada- 



56 AH these statements and quotations, in regard to Cophotis, Sitana, 

 and Draco, as well as the following facts in regard to Ceratophora, are 

 taken from Dr. Gunther's magnificent work on the ' Reptiles of British 

 India/ Ray Soc. 1864, pp. 122, 130, 135. 



Fig. 34.— Ceratophora Stocklartii. 

 Upper figure, male ; lower 

 figure, female- 



