xiii PHYLUM CHORD ATA 339 



Ethology. The Lizards are, for the most part, terrestrial 

 animals, usually extremely active in their movements and en- 

 dowed with keen senses. The majority readily ascend trees, and 

 many kinds are habitually arboreal ; but the Chamseleons are the 

 only members of the group which have special modifications of 

 their structure in adaptation with an arboreal mode of life. The 

 Skinks and the Amphisbsenians are swift and skilful burrowers. 

 The Geckos are enabled by the aid of the sucker-like discs on the 

 ends of their toes to run readily over vertical or overhanging smooth 

 surfaces. A few, on the other hand (Water-Lizards), live habitually 

 in fresh w r ater. The Flying Lizards (Draco) are arboreal, and make 

 use of their wings or, to speak more accurately, aeroplane or para- 

 chute to enable them to take short flights from branch to branch. 

 Chlamydosaurus is exceptional in frequently running on the hind- 

 feet, with the fore-feet entirely elevated from the ground. A 

 tolerably high temperature is essential for the maintenance of the 

 vital activities of Lizards, low temperatures bringing on an inert 

 condition, which usually passes during the coldest part of the year 

 into a state of suspended animation or hibernation. The food of 

 Lizards is entirely of an animal nature. The smaller kinds prey 

 on Insects of all kinds, and on Worms. Chameleons, also, feed on 

 Insects, which they capture by darting out the extensile tongue 

 covered with a viscid secretion. Other Lizards supplement their 

 insect diet, when opportunity offers, with small Reptiles of various 

 kinds, Frogs and Newts, small Birds and their eggs, and small 

 Mammals, such as Mice and the like. The larger kinds, such as 

 the Monitors and Iguanas, prey exclusively on other vertebrates ; 

 some, on occasion, are carrion-feeders. Most Lizards lay eggs 

 enclosed in a tough calcified shell. These they simply bury in 

 the earth, leaving them to be hatched by the heat of sun. Some, 

 however, are viviparous ; in all cases the young are left to shift 

 for themselves as soon as they are born. 



Most of the Snakes are also extremely active and alert in their 

 movements ; and most are very intolerant of cold, undergoing a 

 hibernation of greater or less duration during the winter season. 

 Many live habitually on the surface of the ground some kinds by 

 preference in sandy places or among rocks, others among long 

 herbage. Some (Tree-Snakes) live habitually among the branches 

 of trees. Others (Fresh-water Snakes) inhabit fresh water ; others 

 (Sea-Snakes) live in the sea. The mode of locomotion of Snakes 

 on the ground is extremely' characteristic, the reptile moving 

 along by a series of horizontal undulations brought about by con- 

 tractions of the muscles inserted into the ribs, any inequalities on 

 the surface of the ground serving as fulcra against which the free 

 posterior edges of the ventral shields (which are firmly connected 

 with the ends of the ribs) are enabled to act. The burrowing 

 Blind-Snakes and other families of small Snakes feed on Insects 



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