338 



ZOOLOGY 



SECT;. 



3. GENERAL ORGANISATION OF RECENT REPTILIA. 



External Features. In external form, as in some other 

 respects, certain of the Lacertilia exhibit the least specialised 

 condition to be observed among the living Reptilia. Lacerta is 

 such a central type, and the general account of that Lizard which 

 has just been given applies in all the points of cardinal importance 

 to a large proportion of the Lacertilia. Modifications take place, 

 however, in a variety of different directions. Of such the following 

 are a few of the chief. The tail region is usually, as in the example, 



FIG. 077. Chamaeleon vulgaris, xf. 

 (From the Cambridge Natural History.') 



extremely long and tapering ; but in some groups of Lizards it is 

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

 expanded into a leaf-like form. In the Chameleons (Fig. 977) 

 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 

 Chameleons (Fig. 977) both fore- and hind-limbs become prehensile 



