THE REPTILIA 311 



is extremely slow in its movements. The shell of the turtle 

 consists of bone. It does not really cover the body since it lies 

 beneath a co.at of horny shields. 



Method of Feeding. Of great service to an animal of the 

 turtle's habits of sluggish locomotion is the long, flexible neck 

 which enables it while lying quietly in one place to reach out 

 in any direction for the insects and other small animals upon 

 which it feeds. Some turtles live entirely upon vegetation, 

 which of course can be obtained without rapid locomotion. 

 The large mouth is toothless, but the margins of the jaws are 

 edged with horny plates adapted ^ to cutting. The snapping 

 turtle can bite off a finger and large specimens can even ampu- 

 tate a hand. 



Internal Organs. The turtle's digestive system differs very 

 little from that of the frog. Its heart also consists of the same 

 parts, two auricles and one ventricle, but the ventricle is divided 

 into two chambers by a perforated partition. The young of the 

 turtle as well as the adults breathe with lungs, no gills being 

 present. 



Nervous System. Slight advances in the development of the 

 nervous system over that of the frog are evident in the turtle. 

 The cerebral hemispheres of the brain are larger, and a distinction 

 can be made between an outer gray layer and a central white 

 portion. The cerebellum is also larger, indicating an increase in 

 the power of correlating movements. 



Sense Organs. The eyes are small, with an iris which is 

 often colored. The sense of hearing is fairly well developed, 

 and turtles are easily frightened by noises. The sense of smell 

 enables the turtle to distinguish between various kinds of food 

 both in and out of the water. The skin over many parts of the 

 body is very sensitive to touch. 



Egg Laying. Turtles are bisexual. Their eggs are whitish, 

 spherical, or oval in shape, and covered with a more or less hard- 

 ened shell. They are laid in the earth or sand a few inches from 

 the surface, where they are left to hatch. 



