MIGRATION OF THE LEMMING.
A new theory has been broached to explain the migrations of the Norway lemming, a variety of field mouse. Every few years an immense body of these animals leaves their habitat and proceed westward, attacking every obstacle in front in preference to flanking it, until it reaches the sea, which the little animals boldly enter, only to perish there. No conceivable advantage to the lemming is known to have ever resulted from these long and arduous marches. The losses in swimming large rivers, from fire, the attacks of predatory animals, hunger, and fatigue, are so great that but few reach the sea, and the remnant always perish there. Mr. W. Duppa Crotch, who has studied the habits of these animals for ten years, now suggests that they are moved by an hereditary instinct, and that their prehistoric home was some country west of Sweden, and now covered by the Atlantic. The same kind of reasoning would allot an Atlantic origin to the progenitors of the grasshoppers, which have been such plagues in this country for a few years, for, as stated in the August "Galaxy," those which moved eastward in 1875 did not halt until they perished on the ocean beach or in its waves. Mr. Crotch has thrown new light on some of the habits of the lemming. According to him, says "Nature," the migration is not all completed in one year, as formerly supposed, nor do they, as stated, form processions and cut their way through obstacles; but, breeding several times in the season, they gather in batches, and at intervals make a move westward. Their pugnacity, he states, is astonishing, and the approach of any animal, or even the shadow of a cloud, arouses the anger of this small creature like a guinea pig, and they back against a stone or rock uttering shrill defiance. Our author found, in most examples, a bare patch on the rump, due to their rubbing against the said buttress of support when at bay. He wonders why a bare patch, and not a callosity, should not result from this innate, apparently hereditary habit.