52 REPTILES AND BATRACHIANS 



being united by suture, while in snakes the mouth is 

 highly expansible, the rami of the lower jaw being 

 connected together by an elastic ligament. Apart from 

 this character, the bifid tongue of snakes is invariably 

 retractile within a basal sheath, which is not the case 

 amongst lizards, except Monitors and a few Teiids. 



Lizards present a remarkable variety of types, some 

 being adapted either for climbing, running, swimming, 

 " flying " (parachute bearers), or crawling like snakes, 

 whilst others live underground and have become degener- 

 ate, assuming the appearance and movements of worms. 

 The feet may be adapted for grasping the branches of 

 trees, as in the Chameleons, or they may be provided with 

 adhesive pads, for ascending smooth surfaces, as in the 

 Geckos. The tongue differs to a very great extent in shape, 

 according to its function : it may be broad and short, and 

 merely an organ of taste, as in Geckos and Agamas, or 

 very long and forked, as in Monitors, where it acts as a 

 feeler, while in Chameleons it is extremely exsertile and 

 provided with a sticky club-shaped end, adapted for 

 shooting at insects. 



The tail of many lizards is extremely fragile, and easily 

 broken off, the fragility being evidently of use in allowing 

 them to escape when seized by their enemies. The 

 vertebrae of the tail are divided by a septum into two 

 halves, the breaking taking place at that weak point, and 

 not, as has sometimes been stated, between two vertebrae, 

 which are usually furnished with a socket-and-ball 

 articulation. 



When the tail has been broken, it grows again, sometimes 

 even in a double or triple form ; the vertebrae are, however, 



