46 FIRST LESSONS IN ZOOLOGY 



duck-bills, the lowest of the mammals, the young are 

 born alive — that is, not hatched from eggs laid outside 

 the body — and are nourished after birth, for a shorter or 

 longer time, with milk drawn from the body of the mother. 

 The nests or homes of mammals present varying degrees of 

 elaborateness, from a simple cave-like hole in the rocks 

 or ground to the elaborately constructed villages of the 

 beavers, \\ith their dams and conical several-storied 

 houses. The wood-rat piles together sticks and twigs in 

 what seems, from the outside, a most haphazard fashion, 

 but which results in the construction of a convenient and 

 ingenious nest. The moles and pocket-gophers build 

 underground nests composed of chambers and galleries. 

 The prairie-dogs make burrows in groups, forming large 

 villages. 



We are familiar with the devotion to their young dis- 

 played by birds and mammals. The parent will often 

 risk or suffer the loss of its own life in protecting its off- 

 spring from enemies. Many mother-birds have the in- 

 stinct to flutter about a discovered nest, crying, and 

 apparently broken-winged, thus leading away the preda- 

 tory fox or weasel to fix his attention on them and to 

 leave the nest unharmed. 



See Beard's "Curious Homes and their Tenants." 



