448 



MAMMALIA. 



These animals thus make their way as far sometim.es as Ger- 

 many. Incalculable numbers of them perish during the journeys, 

 and scarcely a hundredth part ever live to return. 



Much discussion has taken place as to the cause which induces 

 the Lemmings, as well as the Hamsters, to undertake these 

 migrations. It has been sometimes asserted that they foresee a 

 hard winter, and that they make these journeys to avoid it. 

 But the more probable supposition is that these changes of abode 

 are owing to a superabundance in their numbers, which naturally 

 leads to a deficiency in the means of subsistence. 



Fig. 183. — Lemming {Hypud<nLsnorvegicus). 



Musquash, or Musk-Rats — Musquash (Fig. 184) are much larger 

 than Rats, their size being equal to that of a smaU Eabbit. 

 They are plentiful all over North America, especially in Canada, 

 and are thoroughly adapted for an aquatic or amphibious life. 

 Their hind-feet are semi-webbed, and each toe is fringed with 

 straight hair; added to this, the tail, which is almost as long as 

 the body, is flattened, and covered with scales. 



They possess a gland which secretes a milky fluid of a pene- 

 trating musky odour ; hence the name Musk-Rats is frequently 

 given them. 



These animals have a highly developed constructive genius. 

 In this they resemble the Beaver, a species which we shall soon 

 consider ; for they combine to build villages, in which they find a 

 safe refuge against cold, and the attacks of their enemies. 



