56 NATURE STUDY IN SCHOOLS. 



of fat stored among the intestines and other internal organs. This 

 fat furnishes nutrition for the animals during their long winter sleep. 



Among the lower animals, few hibernate. Hydras, jelly-fishes and 

 star-fishes retreat into deep water, but are more or less active all win- 

 ter. Marine worms do not appear to hibernate, and while leaches and 

 earth worms retreat below the reach of ice and frost, the former 

 named, into the mud, and the latter, into the earth, I do not think 

 tliev are wholly inactive. 



Among mollusks, we find that land snails in the north pass the 

 winter in a state of inaction which is true hibernation. The animals 

 retreat within their shells and form two or three doors to the en- 

 trance, one behind the other. These doors are formed of a kind of 

 mucus, secreted from glands in the head of the mollusk. I have found 

 the land shells as far south as Southern Florida, thus hibernating, 

 and in the West Indies they do the same thing. 



Few, if any crustaceans, hibernate. Among the insects some 

 beetles, butterflies, and bees hibernate, as will be seen upon con- 

 sulting an article on another page upon this subject. 



Among vertebrates, we find some fishes passing into deeper wat- 

 er, but it is highly probable that none hibernate. 



The same is true of frogs, toads, and salamanders. None of 

 these animals are as active as during warm weather, but I do not think 

 that any of them hibernate. 



All snakes, on the other hand, do hibernate in cold climates. 

 There is an accumulation of fait about the intestines during autumn, 

 upon which the snake subsists in winter. The animals crawl into some 

 sheltered place like a heap of stones which extend some distance into 

 the earth below frost, and then pass the winter in a dormant state. 



If by chance a snake becomes frozen in its retreat, it probably 

 dies. Such at least has been the fate of snakes that I have kept in 

 confinement, when even slightly frozen. Turtles are more or less active. 



Lizards an 1 alligators hibernate in cold climates, the latter named 

 lyiri'4 buried in the mud. 



No birds are known to hibernate, although swallows were once 

 supposed to do so. 



Some mammals hibernate. Among rodents we find that little 

 animal with a reddish yellow back, and very long tail and hind legs, 

 known as the jumping mouse, hibernating. The mouse burrows 

 down into the earth below frost, and then makes a large, round 

 nest of grass, pieces of fibrous bark, etc. In this nest it goes to 

 sleep and remains in this state all winter. I once dug a jumping 



