328 



ZOOLOGY 



SECT. 



comparatively short and thick ; and in others it is depressed and 

 expanded into a leaf-like form. In the Chamaeleons (Fig. 988) 

 the long and tapering tail is used as a prehensile organ, the coiling 

 of which round branches of the trees in which the animal lives 

 aids in maintaining the balance of the body in climbing from 

 branch to branch. 



In the limbs there is likewise a considerable amount of varia- 

 tion in the different groups of the Lacertilia. Moderately long 

 pentadactyle limbs like those of Lacerta are the rule. In the 

 Chamaeleons (Fig. 988) both fore- and hind-limbs become prehensile 



FIG. 988. Chamaeleon vulgaris, x f . 

 (From the Cambridge Natural History.) 



by a special modification in the arrangement and mode of articula- 

 tion of the digits. In these remarkable arboreal Reptiles the three 

 innermost digits of the manus are joined together throughout 

 their length by a web of skin, and the two outer digits are 

 similarly united : the two sets of digits are so articulated that 

 they can be brought against one another with a grasping movement 

 analogous to the grasping movement of a Parrot's foot or of 

 the hand of Man. A similar arrangement prevails in the pes, the 

 only difference being that the two innermost and three outermost 

 digits are united. In some groups of Lacertilia, on the other hand, 

 such as the Blind- Worm (Anguis), limbs are entirely absent, or are 



