OEDEE OF EODENTIA. 
447 
troops, in tlie 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 amphibius) 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 pretty. During 
during daytime they creep into their burrows to enjoy sleep, 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. 
