THE VOLES. 



159 



of the Scandinavian Alps, in Lapland and 

 Finland, it is met with everywhere. It lives 

 like the hamster, and like this kinsman, too, is 

 courageous and vicious notwithstanding its 

 small size. In favourable years it multiplies 

 to such an extent that enormous swarms are 

 compelled to emigrate in order to seek their 

 food elsewhere. In spite of the fact that their 

 habitual mode of life is a nocturnal one, they 



then move on in a close phalanx in the full 

 light of day, swim across brooks and even 

 rivers, and are not deterred by the fact of 

 their being pursued by eagles, falcons, and 

 small carnivores. The carcasses of those 

 which die on the way pollute the air all round. 

 Similar migrations of the brown rat, voles, 

 and other rodents have been observed. 



The Musk-rat, the Musquash of Canada, 



Kig. 217. The Musk-rat or Musquash (Fiber ziiethicus). 



the Ondatra of the Indians (Fiber zibethicus), 

 fig. 217, is a species living entirely in the 

 water. This is a pretty large rat, whose com- 

 pressed and flattened tail, sparsely covered 

 with stiff bristles, is of about the same length 

 as the body. In the neighbourhood of the 

 anus there is a gland of the size of a nut, which 

 secretes an oily substance with a strong smell 

 of musk. The five toes of the hind-feet as 

 well as the four toes of the fore-feet are con- 

 nected by a web set with stiff intercrossing 

 bristles, which are of service in swimming. 

 The coat consists of very fine thick soft 

 woolly hair, beyond which projects a number 

 of long glossy bristles. On the back the 

 colour is brown, on the belly reddish-gray. 

 In Canada it is eagerly hunted for the sake 

 of its very valuable fur. About three millions 

 of skins are obtained every year. The mode 



of life of the musk-rat is similar to that of the 

 beaver. According to circumstances it either 

 excavates tunnels on the steep banks of rivers 

 or constructs regular fortresses with domed 

 roofs rising above the surface of the water; 

 but such fortresses are of course distinguished 

 from those of beavers by their much smaller 

 size. 



We now mention a few mice of which no 

 illustrations are given, but which yet deserve 

 some attention. 



First there is the Australian genus Hy- 

 dromys, which is distinguished from all other 

 rodents by the remarkably small number of 

 its cheek-teeth. In each jaw there are, in fact, 

 only two such teeth ; these have oval enamel 

 folds. This genus lives in the water like the 

 musk-rats. The fore-feet are adapted for 

 burrowing, the hind ones for swimming. 



