CHAPTER XXII. 

 CLASS III. REPTILIA (LIZARDS, CROCODILES, TORTOISES, SNAKES). 



LABORATORY WORK. 



403. Specimens of reptiles are scarcely abundant enough to 

 serve as satisfactory laboratory types for elementary classes, 

 but instructive comparisons may be made by single students 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. 



404. Special Topics for Investigation in the Laboratory. 



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 as an organ? How 

 is the tail to be distinguished 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 

 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. 



405. The Reptilia differ from the vertebrates we have 

 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 compartments (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 



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