308 ELEMENTARY ZOOLOGY. 



(Fig. 123). With the exception of a few sea-turtles, the 

 alligators and crocodiles, and the boas and pythons, all 

 of the living species are small. 



With the exception of snakes, the reptiles are covered 

 with bony scales or plates in such a way as to furnish 

 much protection. In the case of the snakes the scales 

 are thinner, more superficial, and are shed periodically. 



315. Practical Exercise for the Library. By reference to all the 

 pictures and descriptions you can find, supplemented by your own 

 knowledge of these animals, prepare a paralleled column report 

 comparing lizards, alligators, turtles, and snakes in respect to the 

 following points: (i) haunts and general mode of living; (2) kinds 

 of food and means of capturing it; (3) the general form of the body; 

 (4) the appendages their number, position, joints, fingers; (5) the 

 covering of the body and the materials of which it is composed; 

 (6) the mode and efficiency of locomotion; (7) breeding habits and 

 care of young. 



316. Practical Exercise for the Field and Laboratory. Enough 

 specimens of turtles, of snakes, and of lizards can usually be had 

 to enable the members of the class to make some record of observa- 

 tions either in the field, or in the laboratory, or both. The follow- 

 ing and similar topics may be investigated. 



1. What is the effect of changes in temperature upon the activi- 

 ties of reptiles? 



2. What are the differences between the scales of fishes and of 

 snakes? Between those of snakes and lizards? 



3. Can you find evidences of special senses? Where are the or- 

 gans located? What peculiarities seem worth noting? 



4. Tell in detail just how the snakes move. Can they climb trees? 

 How is it done? 



5. Do you find anything to suggest protective coloring? Describe 

 and test. 



6. How many different kinds of snakes, turtles, and lizards are 

 found in your locality? Record any differences of habit and dis- 

 tribution that you discover. Supplement this by reference to the 

 authorities. 



317. Respiration and Circulation. As has been inti- 

 mated, the reptiles are pure air-breathers, and their lungs 



