THE LEMMINGS 



1307 



It is probable that the periodical migrations of the lemmings are induced by a 

 scarcity of food. Brehm remarks that if an early spring following a wild winter 

 is succeeded by a hot and dry summer, everything will be favorable for an un- 

 wonted increase in the number of these animals. The dry summer will, however, 

 equally tend to diminish the quantity of vegetation available for their support, and, 

 accordingly, a migration to more fertile regions will be rendered necessary. Why, 

 however, the migration should be continued in this extraordinary manner is a 

 question which has not yet received a satisfactory answer. The number of lem- 

 mings taking part in a migration has been estimated at many millions, and on such 



r 



NORWEGIAN LEMMINGS MIGRATING. 

 (One-half natural size.) 



occasions every bush and every rock or large stone has a lemming hiding under it, 

 while sometimes even the towns swarm with these creatures. Not only do the 

 lemmings attempt to swim rivers and lakes which are too wide for them to cross, 

 but, writes Mr. T. T. Somerville, "they tumble into holes, wells, and brooks, the 

 sides of which are too steep for them to scramble out of again, so that frequently 

 people are at a loss to obtain water that is not polluted by their bodies. Doubt- 

 less this accounts for an epidemic popularly termed ' lemming fever,' that is 

 said to prevail after the migration, and which is described as resembling ordinary 

 typhoid. ' ' 



