33 



SEXUAL SELECTION. 



[Part II. 



rived at maturity, at whicli age the middle appendage is 

 Bometimes twice as long as the liead. ISIost of the species 

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

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

 the females or young male?." 



There are other and much more remarkable differences 

 between the sexes of certain lizai'd^;. The male of Cerato- 

 j)l(ora 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 terminal scale forms a minute 

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

 third species ( C. Stoddartif, Fig. 34), the whole api)cnd- 



age is converted into a horn, 

 which is usually of a white color, 

 but assumes apur])lish tint when 

 the animal 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. Gunther has 

 remarked to me, may be com- 

 pared with the combs of galli- 

 naceous birds, and apparently 

 serve as ornaments. 



In the genus Chama^leon 

 we come to the climax of dil- 

 ference between the sexes. The v.]i])vt ]iart of the skull 

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



'« All these statements and quotations, in regard to Cophotis, Fitana, 

 and Draco, as well as the followinfi facts in regard to Ceratophora, arc 

 taken from Dr. Gunther's magnificent work on the 'Rc^itiles of British 

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



Fig. 34.— Ccrntophora Stoddartii. 

 Upper figure, male ; lower 

 figure, female. 



