SEXUAL SELECTION 457 



in the rattlesnakes of North America, the male of which, 

 as the keeper in the Zoological Gardens showed me, can at 

 once be distinguished from the female by having more 

 lurid yellow about its whole body. In South Africa the 

 Bucephalus capensis presents an analogous difference, for 

 the female "is never so fully variegated with yellow on the 

 sides as the male. ' ' " The male of the Indian Dipsas cyno- 

 don, on the other hand, is blackish brown, with the belly 

 partly black, while the female is reddish or yellowish olive, 

 with the belly either uniform yellowish or marbled with 

 black. In the Tragops dispar of the same country, the 

 male is bright green, and the female bronze colored." No 

 doubt the colors of some snakes are protective, as shown 

 by the green tints of tree-snakes, and the various mottled 

 shades of the species whicTi live in sandy places; but it is 

 doubtful whether the colors of many kinds, for instance 

 of the common English snake and viper, serve to conceal 

 them ; and this is still more doubtful with the many foreign 

 species which are colored with extreme elegance. The 

 colors of certain species are very different in the adult 

 and young states." 



During the breeding season the anal scent-glands of 

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

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

 lary glands of crocodiles. As the males of most animals 

 search for the 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 her dead body. They are not known to fight together 

 from rivalry. Their intellectual powers are higher than 

 might have been anticipated. In the Zoological Gardens 



» Sir Andrew Smith, "Zoolog. of S. Africa: Reptilia," 1849, pL x. 

 " Dr. A. Giinther, "Reptiles of British India," Ray Soo., 1864, pp. 304, 308. 

 »• Dr. Stoliczlca, "Journal of Asiatic Soc. of Bengal," vol. xxxix., 1870, 

 pp. 306, 311. 



•» Owen, "Anatomy of Vertebrates," voL i., 1866, p. 616. 



