THE REPTILES 207 



supposed to serve for the purpose of defense, and that it is 

 in some way related to the poison-glands. This, however, 

 is an error. The tongue is used primarily as an organ of 



FIG. 120. Tuatera (Sphenodon punctatus). 



touch, and in snakes especially it is almost continually 

 darted in and out to determine the character of the animal's 

 surroundings. 



1 94. Egg-laying. The eggs of the reptiles are relatively 

 large and enclosed in a shell like a bird's egg, the shell, 

 however, being leathery rather than made of lime. These 

 are deposited in some warm situation, and generally left to 

 themselves to hatch. Under stones, logs, and leaves, or 

 buried lightly in the soil, are the positions most frequently 

 chosen by the lizards and snakes. The turtles almost 

 invariably select the warm sand at the edge of the water, 

 and after scooping a hole lay numerous spherical eggs, 

 usually at night. The alligators lay upward of a hundred 

 eggs about the size of those of a goose, and guard them 

 jealously until and even after they hatch. On the other 

 hand, the young of many lizards and snakes are born alive, 

 the eggs being hatched within the body. 



Many reptiles are surprisingly slow in attaining maturity, 

 and live to an age attained by few other animals. It is a 

 well-known fact that turtles live fully a hundred years, and 



