SNAKES, TURTLES, LIZARDS, CROCODILES 265 



can enter the lungs. These animals come to the surface to 

 get air, and the tip of the snout where the nostrils open may 

 often be seen projecting just above the water for this purpose. 



In the spring season the male alligators bellow very loudly. 

 The eggs are laid sometimes in a hollow in the sand, and 

 sometimes in a mound built by the reptile. The eggs are 

 deposited in layers, with grass and sticks between. They 

 are left to be hatched by the sun. Alligators seldom 

 attain a length of twelve feet (Fig. 183). 



Characteristics of this order. — These reptiles are re- 

 garded as the highest of the class, for several reasons. The 

 heart, for example, is divided into four chambers which is 

 much like that of the birds. The brain is more like that of 

 the birds than the brains of other reptiles. The stomach 

 is very birdlike. 



The crocodiles and alUgators are covered with large, bony 

 scales and the limbs are fitted for crawling and swimming, 

 the toes being partly webbed. The jaws are furnished with 

 many conical teeth implanted in sockets, and the eyes are 

 well developed and furnished with three lids. 



Adaptations and habits of the reptiles. — Probably no 

 group of vertebrates offers a more striking example of adap- 

 tations to surroundings in the matter of coloring than 

 snakes. There are the small grass snakes that are green 

 in color to resemble the grass in which they live. Those 

 snakes that live in trees are colored to resemble the bark 

 or the leaves. There is a snake living in India that is per- 

 fectly harmless, yet so closely resembles the hooded cobra 

 in form, color, and markings that it deceives those well 

 acquainted with both. The neck is dilatable like that of 

 the cobra. There can hardly be a doubt that this is a case 

 of protective resemblance. 



