3 12 ELEMENTARY ZOOLOGY 



eyes similar to that of the birds. In addition to the usual 

 eyes there is in many lizards a remarkable eye-like organ, 

 the so-called pineal eye. which is situated in the roof of 

 the cranium, and is believed to be the vestige of a true 

 third eye, which in ancient reptiles was probably a well- 

 developed organ. 



Life-history and habits. Most reptiles lay eggs from 

 which the young hatch after a longer or shorter period of 

 incubation. Usually the eggs are simply dropped on the 

 ground in suitable places (although certain turtles dig 

 holes in which to deposit them), where they are incubated 

 by the general warmth of the air and ground. However, 

 some of the giant snakes, the pythons for instance, hold 

 the eggs in the folds of the body. In the case of some 

 snakes and lizards the eggs are retained in the body of 

 the mother until the young hatch; such reptiles are said 

 to be ovoviviparous, because the young, although born 

 alive, are in reality enclosed in an egg until the moment 

 of birth. Among reptiles the newly hatched young 

 resemble the parents in most respects except in size, yet 

 striking differences in coloration and pattern are not rare. 

 But there is in this class no metamorphosis such as 

 characterizes the post-embryonic development of the 

 batrachians. 



The food of reptiles consists almost exclusively of 

 animal substance, although some species, notably the 

 green turtles and certain land-tortoises, are vegetable- 

 feeders. The animal-feeders are mostly predaceous, the 

 smaller species catching worms and insects, while the 

 larger forms capture fishes, frogs, birds, and their eggs, 

 small mammals, and other reptiles. 



Classification. The living Reptilia are divided into 

 four orders, of which one includes only a single genus, 

 Hatterin, a peculiar lizard found in New Zealand. The 

 other three are the Squamata, which includes the lizards 



