336 THE ZOOLOGIST. 



THE ECDYSES OF SNAKES; AS OBSERVED 

 IN BRITISH INDIA. 



By R. M. Dixon. 



The skin in Snakes, as in other vertebrates, consists of two 

 layers, namely, a superficial (ectodermal) and a deeper (meso- 

 dermal) layer. These two layers are respectively known as the 

 epidermis, or scarf-skin, and the dermis, or true skin. The 

 dermis is also known as the derm, derma, cutis, or corium. In 

 the epidermis there are two layers. The outer layer consists of 

 horny cells, and is termed stratum corneum, or the horny layer. 

 The inner layer is composed of protoplasmic cells, and is known 

 as stratum Malpighii, or the mucous layer. The inner layer 

 always serves as a matrix for the formation of the horny layer, 

 which is periodically cast off as one entire piece. The casting 

 off of the horny layer of the epidermis, unaccompanied by organic 

 development, is technically known as ecdysis. Ecdysis is a 

 simple moulting as in Snakes, and is quite distinct from meta- 

 morphosis, which is a change in form or structure resulting from 

 development, as in insects. The process of ecdysis in Snakes is 

 just the same as what happens in the case of mankind, only 

 human beings " shed their skins" bit by bit, almost every hour, 

 while Snakes shed theirs as one coherent piece at periodical 

 intervals. The moulting of feathers in birds is done on the 

 same principle. The ecdyses of Snakes resemble the ecdyses of 

 Crustaceans in a remarkable degree. The Common Crayfish 

 (Astacus Jluviatilis) of Europe has been known to moult its skin 

 several times in the year, and I have noticed the Indian Rock- 

 Lobster (Palinurus vulgaris) shed its skin as one entire piece. 



In all the Ophidia, over the surface of the eye, there is a thin 

 invisible miniature watch-glass-like capsule, which peels off with 

 the horny layer of the epidermis when that is shed. When the 

 time to moult the horny layer of the epidermis approaches, the 

 Snake looks dull and drowsy. The usual colour of the body 



