354 The Descent of Man. Part II. 



attack them. Nor can T quite disbelieve the several accounts 

 which have appeared of their thus paralysing their prey with fear. 

 Some other snakes also make a distinct noise by rapidly vibrating 

 their tails against the surrounding stalks of plants ; and I have my- 

 self heard this in the case of a Trigonocephalus in S. America. 



Lacertilia— -The males of some, probably of many kinds of 

 lizards fight together from rivalry. Thus the arboreal Anolis 

 cristatettus of S. America is extremely pugnacious : " During the 

 " spring and early part of the summer, two adult males rarely 

 " meet without a contest. On first seeing one another, they nod 

 " their heads up and down three or four times, and at the same 

 " time expanding the frill or pouch beneath the throat ; their 

 " eyes glisten with rage, and after waving their tails from 

 " side to side for a few seconds, as if to gather energy, they dart 

 " at each other furiously, rolling over and over, and holding 

 " firmly with their teeth. The conflict generally ends in one of 

 " the combatants losing his tail, which is often devoured by the 

 '* victor." The male of this species is considerably larger than 

 the female ; 65 and this, as far as Dr. Giinther has been able to 

 ascertain, is the general rule with lizards of all kinds. The 

 males alone of the Cyrtodactylus rubidus of the Andaman Islands 

 possesses pre-anal pores ; and these pores judging from analogy 

 probably serve to emit an odour. 66 



The sexes often differ greatly in various external characters. 

 The male of the above-mentioned Anolis is furnished with a 

 crest which runs along the back and tail, and can be erected at 

 pleasure ; but of this crest the female does not exhibit a trace. 

 In the Indian Cophotis ceylanica, the female has a dorsal crest, 

 though much less developed than in the male ; and so it is, as 

 Dr. Giinther informs me, with the females of many Iguanas, 

 Chameleons, and other lizards. In some species, however, the 

 crest is equally developed in both sexes, as in the Iguana tubercu- 

 latum In the genus Sitana, the males alone are furnished with a 

 large throat-pouch (fig. 33), which can be folded up like a fan, 

 and is coloured blue, black, and red ; but these splendid colours 

 are exhibited only during the pairing-season. The female does 

 not possess even a rudiment of this appendage. In the Anolis 

 cristateUus, according to Mr. Austen, the throat pouch, which is 

 bright red marbled with yellow, is present in the female, though 

 in a rudimental condition. Again, in certain other lizards, both 

 sexes are equally well provided with throat pouches. Here we 



65 Mr. N. L. Austen Vept these 66 Stoliczka, 'Journal of Asiatic 



animals alive for a considerable Soc. of Bengal,' voi. xxxiv. 1870, p. 



time ; see ' Land and Water,' * uly 166. 

 1867, p. 9. 



