MAMMALS. 



363 



immigrant, the English sparrow. Among these singing 

 birds are some which, like the crows, are not noted for 



FIG. 156. Winter Wren. From Couea. 



their musical abilities, and their near relatives, the birds 

 of paradise. We can only mention, in addition, the star- 

 lings, flycatchers, wrens, orioles, warblers, and thrushes, 

 forms which make our woods and fields vocal and beautiful. 



GRADE III. MAMMALIA (MAMMALS). 



The name Mammalia is applied to all those forms which, 

 like the mouse, cow, and man, have warm blood, a body 

 covered with hair, and which bring forth living young, 

 nourished during the early stages by milk secreted by the 

 mother. These characters at once distinguish any mam- 

 mal from any other animal, but other features of equal or 

 greater importance occur. 



Hair occurs in the young of all mammals, and is usually 

 found also in the adult; but in the case of the whales it is 

 absent in the fully grown animal, and even in the young it 

 is only found near the mouth. Hair is a product of the 

 outer or epidermal layer of the skin. At places this layer 



