60 REPTILES 



species, the change is gradual and imperceptible. In other 

 instances the shift is more marked, as in the changing of the 

 hair in many mammals in spring and autumn, and the " moult " 

 of birds. In certain reptiles — namely snakes and lizards — (as 

 well as in amphibians) alone is the entire epidermis, inclusive 

 even of that covering the cornea of the eye, sloughed at once, 

 either, as in the case of snakes, entire, or in several pieces. In 

 describing the change of skin in the common slow-worm, Dr. 

 G. Leighton, in his " British Lizards" writes as follows: — 



" The slough is exceedingly delicate and therefore torn with 

 great ease, and can only be shed entire if the slow-worm is 

 able to glide through soft material during the process of chang- 

 ing. Any sharp projecting point rubbing against the sides of 

 the creature will inevitably tear the slough before it is com- 

 pletely removed. The process starts at the jaws, and the 

 lizard gradually crawls out of the slough, leaving it turned in- 

 side-out as a rule, though the terminal portion of the tail-slough 

 may slip off unreversed. After sloughing, the slow-worm, like 

 other reptiles, is more lively and feeds readily. The length of 

 time between successive sloughings varies. Sloughing always 

 happens after the slow-worm comes out of its winter-quarters, 

 and is generally repeated at intervals of six weeks or so during 

 the months in the year when active life is in progress. The 

 colouring of the reptile is more brilliant after sloughing than at 

 other times. The slough is never eaten by lizards [and snakes], 

 as is the habit of some amphibians." 



The number of times in the year in which certain Indian 

 snakes shed their skins while in captivity is recorded on p. 48 ; 

 and in these it would seem that the change is less frequent 

 than in the slow- worm. In tropical countries it is no uncommon 

 thing to find the complete slough of a python or other large 

 snake from 6 to 10 feet in length. 



In terrapins, and probably in other chelonians as well, a 

 more incomplete, although at the same time a well-marked, 

 change of the superficial layer of the skin takes place. In the 

 case of the freshwater painted terrapin {Clemmys picta), for ex- 

 ample, a thin transparent layer, like a film of mica, peels off all 

 the heavy plates of the shell in autumn or at midsummer, when 

 the brilliant colours underlying the newly formed plates ap- 

 pear much more vivid than ordinary. 



