REPTILES. 187 



though in hot countries nearly all are oviparous. Snakes 

 and Lizards cast their skins periodically at least once a 

 year and generally make a meal of the old coat. As in 

 other creatures that change their skins, the colours of the 

 new coat are brighter than those of the old, and at this 

 period the animal is very susceptible to cold. The skin in 

 Snakes is covered with what appear to be scales, but really 

 each of these is a flattened fold, or pocket, in the true skin, 

 and the outer covering of each will be found intact, forming 

 part of the cast "slough." The truth of this is evident if 

 the skin of a snake and fish be rubbed ; it will be found im- 

 possible to remove the projections on the snake's skin, while 

 the scales of the hsh (being only outside appendages to the 

 skin), rub off easily. The teeth are generally conical and 

 simple, and fixed to the jaws by a bony cement instead of 

 being inserted in sockets. The eyes are provided with eye- 

 lids in the Lizards, but Snakes have an immovable covering 

 like the cover-glass of a watch. Snakes have no external 

 traces of limbs, but there is evidence that they are descended 

 from an ancestral type that had limbs, as some of them 

 possess internal rudiments of legs. Reptiles, being cold- 

 blooded, are of a sluggish disposition, and except when 

 roused by hunger or other passion, display little vitality. 

 Cold weather makes them sleepy, and they then retire into 

 holes, and coil up to keep themselves as warm as possible : 

 frequently several are found together rolled up into a ball. 

 In England they usually come abroad for only the six 

 warmer months of the year, sleeping through the remainder 

 of the time. The vertebral column is always long, and, in 

 some of the Snakes, contains a very large number of vertebrae. 

 The feet, when present, are usually provided with five toes, 

 without claws. Most writers state that Lizards have the 



