THE LIFE OF MAMMALS 
claws; and the beadlike eyes seem always to notice objects 
above them rather than those in any other direction. During 
the summer they form their nests under stones, and in winter 
push long galleries through the turf and under the snow in 
search of their vegetable food, since they lay up no stores. 
“In England,” 
says Crotch, who 
contributed a 
most observing 
account of the 
animal to The 
Popular Science 
Review, new se- 
ries, Volume I, 
page 143, “ 
fail to perceive 
how much active 
life goes on be- 
neath the snow, 
which in more 
northern latitudes 
forms a warm 
roof to numerous 
birds, quadrupeds 
and land insects, which are thus enabled to secure an otherwise 
impossible sustenance. At the same time... a fearful struggle 
for existence is carried on during the long autumnal nights 
before the snow has become a protection rather than a new 
source of danger to all save predaceous animals.” 
At intervals, averaging about a dozen years apart, lemmings 
suddenly appear in cultivated districts in central Norway and 
Sweden, where ordinarily none live, and in a year or two mul- 
tiply into hordes which go traveling straight west toward the 
Atlantic, or east toward the Gulf of Bothnia, as the case may 
434 
we 
NORWEGIAN LEMMINGS. 
