STUDY OF REPTILES 119 



would be absurd ; it is not a casting of the scales, it is a casting 

 of the outermost horny layer of the epidermis. The peculiarity 

 of this moulting for such it is is that the whole slough remains 

 coherent. The shedding begins at the lips, and the husk is turned 

 inside out from before backwards, so that the tail is the part 

 last moulted. No one can forget his first delight at finding a 

 snake's slough, with its suggestion of ghostly chain-armour. It 

 bears the impress of all the details of the scales, even of the 

 watchglass-like scale over the eye. 



In this connection it would be interesting to show the rattle 

 of a rattle-snake, that remarkable musical instrument by which 

 this deadly snake produces in its excitement a shrill whistle- 

 like sound. The noise warns off animals such as peccaries, which 

 are far too large for the rattle-snake to use. It may bite them 

 and kill them, but this means fatigue and the risk of breaking a 

 tooth, all to no purpose. When the rattle-snake moults, the 

 horny covering of the tip of the tail is moulted but remains 

 attached ; at the next moult a second joint is interpolated be- 

 tween the first and the end of the tail. Thus the rattle " grows," 

 sometimes gaining three joints in a year. The total number 

 does not become large, because the terminal parts get broken 

 or worn off. The rattle is usually procurable from dealers in 

 natural history specimens. 



The kind of study which we have thus tried to suggest by 

 particular reference to the snake may be repeated in reference to 

 slow-worm and lizard and tortoise. 



BIBLIOGRAPHY. Hans Gadow, "Amphibia and Reptiles/' vol. viii. of Cambridge 

 Natural History (Macmillan & Co., London, 1901). See also Bell's British Reptiles 

 (London, 1849) ; Leighton's British Serpents (Blackwood, Edinburgh, 1901) ; M. C. 

 Cooke, Our Reptiles and Batrachians (Allen London, 1893). 



