MAMMALS. 
15 
form the second class. Then we have lizards and 
other reptiles to form the third; while the fourth 
consists of frogs and other creatures, that have a 
fish -like life at first, and afterwards a life on 
land. 
10. “ There is one other class to complete the sub- 
kingdom of the backboned animals. Perhaps you 
can name it.” 
“It must be fishes,” cried Arthur; “they are 
different from all the rest, for they can live only 
in the water.” 
n. “ You are right,” said Mr. Johnson. “ Fishes* 
form the fifth class. 
“ Now let us walk home, and, if you will come to 
my house to-morrow afternoon, we will have a long 
talk about the large class to which we and Rover 
belong.” 
MAMMALS. 
1. The next day their friend gave the boys a 
hearty welcome, and led them at once into a room 
well stocked with specimens of his “four-footed 
friends”, as he called them. “ Though that name 
will not do for all of them,” he added; “for there 
you see some monkeys, which I might call ‘ four- 
handed’, because they are able to use their feet 
like hands for grasping things. 
2. “I promised that we would talk only of mam- 
