38 FOUR-FOOTED AMERICANS 



THE VERTEBRATE BRANCHES OF THE ANIMAL 

 TREE 



ANIMALS HAVING BACKBONES 



Animals with bony skeletons; never having more than two 

 pairs of limbs. These animals inhabit both land and water, and 

 may either swim, fly, crawl, or walk. 



Fishes .... Cold-blooded animals that live in water; usually 

 covered with scales. They breathe through gills, 

 and in their fins we see the very l)egiunings of 

 limbs. 



Frogs, etc. . . (Amphibians.) Going through several transforma- 

 tions, from egg to perfect animal, but having legs 

 when fully grown. The stepping-stones between 

 fishes and reptiles. 



Reptiles . . . Cold-blooded, egg-laying animals, either with a shell 

 or scaly covering, living on land or in the water; 

 some kinds doing both. They have simple, three- 

 chambered hearts. Alligators, Turtles, and Snakes 

 are Reptiles. 



Birds Warm-blooded, air-breathing animals. They are 



covered vrith feathers, have four-chambered hearts, 

 and the young are hatched from eggs. 



Mammals . . The highest order of animals. ^\'arm-blooded, air- 

 breathing, having a four-chambered heart and 

 double circulation. The young are born alive and 

 nourished by their mother's milk. INIammals are 

 all more or less covered with hair. The AVhale, 

 Seal, Cat, Cow, Dog, Rabbit, blouse. Bat, Monkey, 

 and !Man are Mammals. 



" The Mammal branch is so large and important and 

 ha.s .so many small Ijranches and twigs of its own that 

 hy and by I shall make you a tree of it by itself." 



" Are you going to draw the ^lanunal tree to-night?" 

 asked Dodo, anxiousl)% " Because I think my head is 

 as full of thinking as it will hold," 



