CHAPTER XXII 



CLASS REPTILIA (Crocodiles, Turtles, Lizards, Snakes) 



Laboratory Work 



411. Specimens of reptiles are scarcely abundant enough to 

 serve as satisfactory laboratory types for elementary classes, 

 but instructive comparisons may be made by individual stu- 

 dents or by groups of students. These results should be 

 reported to the class. 



Prepare three parallel columns, one for the lizard, one for 

 the snake, and one for the turtle. Select a specimen of each 

 and compare them with regard to their haunts; habits; food; 

 general form of body; appendages, number, position, joints, 

 digits ; covering ; manner of locomotion. 



412. special Topics for Investigation in the Laboratory and Field. 



1. Are reptiles warm or cold blooded? Your evidences? 



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



3. In what various ways is the tail of reptiles used? How is the tail to be dis- 

 tinguished from the rest of the body? 



4. What special senses do reptiles possess? What are your evidences? What 

 peculiarities have the organs of sense? 



5. What peculiarities do the internal organs of the snake have which to you 

 seem to be correlated with the slender, elongate form of the animal? 



6. What species of snakes, turtles, and lizards are found in your locality? 

 Report on the special habits of each species in so far as you can determine them 

 by observation. Supplement by reference to authorities. 



Descriptive Text 



413. The Reptilia differ from the vertebrates hitherto studied 

 in the fact that at no period of life do they possess gills. They 

 agree with the lower forms in being cold-blooded and in the 

 incomplete separation of the heart into right and left compart- 

 ments (except in the crocodiles). They are, in addition to 

 their air-breathing habit, similar to the birds and mammals 

 in possessing the protective embryonic membranes known as 



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