32 
SEXUAL SELECTION. 
Part IT- 
thought dangerous by their enemies. The cause, how- 
ever, of the bright colours of the venomous Elaps 
remains to be explained, and this may perhaps be 
sexual selection. 
Lacertilia . — The males of some, probably of many 
kinds of lizards light together from rivalry. Thus the 
arboreal Anolis cristatellus of S. America is extremely 
pugnacious: “During the spring and early part of the 
“ summer, two adult males rarely meet without a con- 
“ test. On first seeing one another, they nod their heads i 
“ up and down three or four times, at the same time 
“ expanding the frill or pouch beneath the throat ; their 
“ eyes glisten with rage, and after waving their tails I 
“ 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 fe- ! 
male ; 65 and this, as far as Dr. Giinther has been able to 
ascertain, is the general rule with lizards of all kinds. 
The sexes often differ greatly in various external 
characters. The male of the above-mentioned Anoiis 
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 
GojAiotis ceylanica, the female possesses a dorsal crest, 
though much less developed than in the male; and 
so it is, as Dr. Gunther 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 tubereulata. In the genus 
55 Mr. N. L. Austen kept these animals alive for a considerable time 
see ‘ Land and Water/ J uly, 1867, p. 9. 
