ORDEE OF EODENTIA. 447 



troops, in the spring of some years they go straight ahead, crossing 

 every obstacle — rivers, arms of the sea, and mountains, leaving 

 behind them numbers of stragglers and exhausted victims, who 

 fall a prey to the crowd of carnivorous animals which follow in 

 their rear. After their journey they are so fatigued that they can 

 scarcely move. At the beginning of winter they return to their 

 homes, and the natives of Kamtschatka make quite a festival in 

 honour of their arrival. 



The Water Rat [Arvicola amphibhis) is another species of this 

 genus, about the size of the Black Rat, and frequents the edges of 

 streams. It swims with ease, and feeds on roots and various 

 aquatic plants. It digs a burrow in the river-bank, of no great 

 depth, but provided with several holes for egress. It is found 

 all over Europe, in Asia, and also, it is said, in America. 



There are various other species of this genus, but an account of 

 them would not furnish us with any fresh peculiarities. 



Lemming. — The Lemmings, the most curious species of this 

 group, are natives of the mountains of Lapland, where they feed 

 on mosses and lichens. Their tail, paws, and claws are all very 

 short. They are about the size of the Rat, and their coat, 

 variegated with black, yellow, and white, is very prettj^ During 

 during daytime they creep into their burrows to enjoy sleejD, but 

 the night they are very active. When they are attacked they 

 defend themselves both with their teeth and claws, and if an 

 attempt is made to catch hold of them, they utter shrill cries. 



At very irregular dates the Lemmings migrate in immense 

 numbers, and make their way towards the south in crowded 

 columns. It seems as if they were drawn on by some irresistible 

 power towards a certain fixed point, so straight is the character 

 of their march. They never go round any obstacle, except when 

 it is absolutely impossible to surmount it ; and then, as soon as the 

 impediment is passed, they again take their former direction. If 

 a large rick of hay happens to stand in their path, they bore right 

 into it, and make a thoroughfare through it. If a boat is moored 

 in a river, and thus crosses their direct road, they will climb over 

 it, and take to swimming again on the other side of it. They 

 only travel at night and in the early morning. Woe be to the 

 field in which they make their halting-place, for it will be left 

 completely bare. 



