174 SUBKINGDOM TERTEBKATA. 



by ball-and-socket joints. The eyes are destitute of lids, and 

 hence the unblinking stare of a serpent. Some species are 

 hatched from the egg before it is deposited, and are said to 

 be ovo viviparous ; but nearly all lay eggs in the sand, to be 

 hatched by solar heat. In some varieties, the mother looks 

 after her young for a season, and swallows them in case of 

 danger. The teeth point backward. Most of the venomous 

 serpents have, in place of teeth in the upper jaw, two fangs, 

 through which the poison is ejected to the bottom of the 

 wound.* The jaws are fastened with elastic ligaments. 



Fig. S95. 



Skeleton of a Sej-pent. 



which allow them to be separated, so that the snake can 

 swallow an animal twice its own size. Snakes shed their 

 epidermis once, and, in many cases, three or four times a 

 year. It parts aroi^nd the mouth, and the reptile slides out 

 of it by crawling through a crevice to hold it, reversing the 

 cuticle. The slough is perfect, even to the epidermis of the 



* Snakes, in repo^f , coil with the tail in the middle and the head outside, laid 

 over, at times, across the folds of the Ijody to the centre of the coil ; so that on an 

 alarm they ran uncoil with a forward motion, as they have no power of moving tail 

 first. \\'hen ahont to strike, resting upon the latter third of their body, they double 

 themselves int'i folds, not coils, and sitddenly Btraighteninff, reach forward their 

 length only, and always instantly recover their darting position. 



