GECKOS, LIZARDS, AND CHAMELEONS. 77 



conspicuous diversity in the matter of adapta- 

 tion to environment, and for the capture of 

 food. Adaptations which are expressed in 

 structural modifications, sometimes of a very 

 profound character. In all this they differ 

 conspicuously from the Crocodiles and Tortoises, 

 which are peculiar, rather on account of the 

 uniformity they display in their organisation. 



In the matter of the capture of food a few 

 examples will suffice. In the case of Lizards 

 which feed upon living animals the prey is 

 seized, generally, by a snapping motion of the 

 jaws, and passed whole down the throat, nob 

 torn in pieces, as with the Crocodiles. Adapta- 

 tions indeed for tearing prey are conspicuous 

 by their absence. Some of the former, however, 

 seize their victims by a lightning thrust of the 

 tongue, and among these the Chamseleons come 

 easily first. In these creatures the tongue 

 attains a great length. Covered with a sticky 

 secretion, this organ is expelled with a dart- 

 like motion and unerring accuracy, so that a 

 fly can be taken at a distance of five or six 

 inches from the tip of the creature's snout. 

 Only in two species of lizards belonging to 

 the genus Heloderma is the prey killed by 

 poison. This is injected, as in the case of 

 Snakes, by means of grooved teeth, which 

 convey the deadly secretion from the large 

 glands in which it is formed, but whilst in 

 the snakes the poison is transmitted through 

 certain teeth in the upper jaw, in these lizards 

 it is conveyed through certain teeth in the 

 lower jaw. The herbivorous lizards of the 



