96 PRACTICAL ZOOLOGY. 



4. The fore limb has, in the upper-arm, the humerus; in 

 the forearm the radius (same side as the thumb) and 

 the ulna; in the wrist are several small bones, the 

 whole collectively called the carpus \ in the hand are 

 the digits. 



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

 a bone which shows, by grooves near its ends, that it 

 is formed by the union of 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 ? 



THE DEVELOPMENT OF THE FKOG. 



By wading into a pond where there are frogs, in the 

 spring, one can usually see how the eggs are laid. If these 

 eggs are watched, they will be seen to produce tadpoles ; 

 the tadpoles may be reared ; at first the form is fish-like, 

 not only in external form, but in the fact that the tadpole 

 has no lungs, but breathes by gills. An opening may be 

 seen on one side, through which water leaves the gills. 

 Later, the lungs develop, and the gills disappear. How do 

 the gills of a tadpole compare with those of a fish ? Is the 

 tadpole a fish ? 



Put a small tadpole in a watch-crystal containing water ; 

 examine the gills under a one-inch objective to see the 

 circulation of the blood through them. Has the tadpole 

 teeth ? Examine its mouth ; what does the tadpole eat ? 

 Open a large tadpole, and observe the long, coiled intestine. 



