202 



ANIMAL BIOLOGY 



(Fig. 368) in respect to the following : Bones of arm 

 (length and shape), fingers, claws, shoulder bones, breast- 

 bone (why with ridge like a bird ?), vertebrae (why are the 

 first two so large ?), skull (shape). There are no eye 

 sockets, but there is a snout gristle ; for the long, sensitive 

 snout must serve in place of the small and almost useless 

 eyes hidden deep in the fur. Is the fur sleek or rough ? 

 Why ? Close or thin ? It serves to keep the mole clean. 

 The muscles of neck, breast, and shoulders are very 

 strong. Why ? The mole eats earthworms as well as 

 insects. It injures plants by breaking and drying out 

 their roots. Experiments show that the Western mole will 

 eat moist grain, though it prefers insects. If a mole is 

 caught, repeat the experiment, making a careful record of 

 the food placed within its reach. 



FIG. 369. SKELETON OF BAT. 



As with the mole, the skeletal adaptations of the bat 

 are most remarkable in the hand. How many fingers ? 

 (Fig. 369.) How many nails on the hand? Use of 

 nail when at rest ? When creeping ? (Fig. 369.) In- 

 stead of feathers, the flying organs are made of a pair 

 of extended folds of the skin supported by elongated 

 bones, which form a framework like the ribs of an um- 

 brella or a fan. How many digits are prolonged ? Does 



