124 THE MEANING OF EVOLUTION 



deadly work as almost any instrument of destruction 

 known to animals below the grade of man. But, after 

 all, this is an old-fashioned method, and the rhinoceros 

 is a relic. 



Among the carnivorous animals the teeth, which 

 were developed first chiefly for the tearing of flesh in 

 its consumption, became effective for their courageous 

 owners. Because these tearing teeth are well devel- 

 oped in the dog they have come to be known as canine 

 teeth. Usually where an animal can use its teeth ef- 

 fectively for ofYense or defense, it is the canine teeth 

 that are thus modified. The cat has developed them 

 better than the dog, and one of the cats of a bygone 

 geological period had canine teeth so magnificently 

 enlarged and so sharp at the back as to give this 

 frightful creature the name of the saber-toothed tiger. 

 The long teeth in the upper jaws of the elephant, com- 

 monly known as tusks, are not canine teeth. The ele- 

 phant has completely lost his canines. His tusks are 

 his incisors, and they have developed as have almost 

 no other teeth in the mammals. 



These are only a few of the numberless devices na- 

 ture has evolved for furthering the success of her chil- 

 dren. There are so many others that to many of us 

 they form almost the chief point of interest in our 

 study of a new animal, or our closer observation of an 

 old friend. 



