PRACTICAL ZOOLOGY ' 43 



the tongue ; the sticky saliva and its use ; the absence 

 of a neck. 



Dissect away the skin and study the shape and 

 attachments of the underlying muscles. Open the 

 abdomen and study the arrangement of the internal 

 organs, the digestive, circulatory, respiratory, excretory, 

 and reproductive systems (Figs. 273, 282); the structure 

 of the heart. Open the skull and examine the brain 

 (Fig. 337) ; trace the course of the principal nerves. 

 Study the principal parts of the skeletal system and 

 compare with that of the fish (Fig. 284). Examine 

 the circulation of the blood as seen in the web of the 

 foot (Fig. 263). Study the corpuscles in a drop of fresh 

 blood (Figs. 260, 261). 



Collect the eggs of frogs or toads in the spring, keep 

 them in an aquarium, and watch the development of the 

 tadpole. Have a series of tadpoles showing the gradual 

 metamorphosis into the adult stage. 



Draw attention to the changes of structural adapta- 

 tion necessitated by the change from the aquatic to the 

 aerial mode of life. 



Turtle 



Water or land turtles may be used, and may be kept 

 alive indefinitely in a damp box in the laboratory. 



Field, Vivarium, and Aquarium Study. On some of 

 the field excursions look for turtles in their native haunts, 

 and learn as much as possible of their habits. In the 

 laboratory note how the turtle walks, its clumsy motions, 

 rate of speed ; the motions of and positions taken by its 

 head, legs, tail ; movements of the eyelids, nostrils ; the 

 respiratory movements. Put the turtle into water and 

 watch its movements when swimming and diving. 



Structure. Study the external covering, its structure, 

 color, and modifications on the body, head, legs, and tail ; 



