CLASS MAMMALS. 359 



11. What is the difference between claws, nails, and 

 hoofs? 



12. What is the nature of horns among mammals? 

 Which bear them? In what various ways do they differ? 

 Compare the mode of growth and structure of a cow's 

 horn with that of the antlers of deer. 



13. Make spring studies of the behavior of mammals. 



