92 REPTILES AND BATRACHIANS 



ences reside in the large eyes, covered by a thick eyelid, 

 pierced with a small central opening for the pupil, and 

 movable independently, turning in every direction ; in 

 the fingers and toes, v^hich are united in tv7o bundles 

 opposable to each other to form a grasping organ, with two 

 digits on one side and three on the other ; and in the tongue, 

 which is club-shaped, sheathed at the base, sticky at the 

 end, and projectile through the action of special muscles 

 to a length exceeding that of the creature's body, an 



Fig. 5. — Head of Cha?neleon calcaratus. 



(, After Boulenger.') 



adaptation for catching the insects on which the lizard 

 feeds. The head as a rule forms a bony casque, sur- 

 mounted with crests or tubercles, while the snout of the 

 males, in some species, is provided with long and pointed 

 horny or bony appendages, which, it has been suggested, 

 may be of use during the breeding season on the assumption 

 that they fight amongst themselves for the possession of 

 the females. The compressed body and very prehensile 

 tail are covered with granules or tubercles ; dorsal and 

 ventral crests are sometimes present. 



