Amphibia. 93 



wrist are several small bones, the whole collectively called the 

 carpus ; in the hand are the digits. 



5. The hind limb has, in the thigh, the femur; in the leg, a 

 bone which shows, by grooves near its ends, that it is formed by 

 the union of the two bones corresponding to the tibia and fibula 

 of man ; the several small bones of the ankle are together called 

 the tarsus ; the bones of the toes are the digits. 



6. Are there any ribs ? 



STUDY OF A TADPOLE. 



Get a number of frog's eggs and place them in a jar of water. 

 If many eggs are placed in a small amount of water, the eggs are 

 not likely to develop well. Set different jars in different places 

 with regard to light and heat, and note any differences in results. 

 It is best to have some aquatic plants in the jar, especially after 

 the young have hatched out. How long before the tadpole within 

 the egg begins to move? How long till it breaks away from the 

 egg mass ? How early do the gills show themselves ? What are 

 the parts of the tadpole? What is the shape of the tail? What 

 is its use ? How is it used ? How early do legs appear ? Which 

 legs develop first? Is there any reason for this? Are tadpoles 

 relatively active or inactive ? Do they move much " of their own 

 accord"? Or chiefly when they are disturbed? Does the tail fin 

 have supporting rays like the fin of a fish? What do tadpoles eat? 

 How do they eat? Have they teeth? Is the growth slow or 

 rapid ? 



Put a tadpole in a watch glass of water under the microscope, 

 with a half-inch or two-thirds-inch objective, and watch the cir- 

 culation of blood in the gills. What becomes of the gills? Watch 

 the sides of the body for a hole where water escapes. Where is 

 it? Why is the tadpole not symmetrical in this respect? What 

 becomes of the tail as the tadpole becomes a frog? 



Examine a dead tadpole to see if there are teeth. What is the 

 size of the mouth in proportion to that of the adult? Look again 

 for the hole on one side of the body. Are there ever limbs con- 



