30 SEXUAL SELECTION. Part IL 



In the Trago]ps dispar of the same country, the male is 

 bright green, and the female bronze-coloured.^" No 

 doubt the colours of some snakes serve as a protection, 

 as the green tints of tree-snakes and the various mottled 

 shades of the species which live in sandy places ; but 

 it is doubtful whether tbe colours of many kinds, for 

 instance of the common English snake or viper, serve 

 to conceal them ; and this is still more doubtful with 

 the many foreign species which are coloured with ex- 

 treme elegance. 



During the breeding-season their anal scent-glands 

 are in active function ;^^ and so it is with the same 

 glands in lizards, and as we have seen with the sub- 

 maxillary glands of crocodiles. As the males of most 

 animals search for tlie females, these odoriferous glands 

 probably serve to excite or charm the female, rather 

 than to guide her to the spot where the male may be 

 found.^^ Male snakes, though appearing so sluggish, 

 are amorous ; for many have been observed crowding 

 round the same female, and even round the dead bodv 

 of a female. They are not known to fight together 

 from rivalry. Their intellectual powers are higher than 

 might have been anticipated. An excellent observer 

 in Ceylon, Mr. E. Layard,'^^ saw a Cobra thrust its head 

 through a narrow hole and swallow a toad. "With 



^0 Dr. A. Gunther, ' Eeptiles of British India,' Eay Soc. 1864, p. 

 304, 308. 



5^ Owen, ' Anatomy of Yertebrates,' vol. i. 186G, p. 615. 



^2 The celebrated botanist Schleiden ineidently remarks ('Ueber 

 den Darwinismus : Unsere Zeit,' 1869, s. 269), that Rattle-snakes use 

 their rattles as a sexual call, by which the two sexes find each other. 

 I do not know whether this suggestion rests on any direct observations. 

 These snakes paii- in the ZooU)gical Gardens, but the keepers have 

 never observed that they use their rattles at this season more than at 

 any other. 



53 "Rambles in Ceylon," 'Annals and Mag. of Nat. Hist.' 2nd series, 

 vol. ix. 1852, p. 333. 



