are drowned in the same manner. They are followed in their
journeys by bears, wolves, and foxes, which prey upon them incessantly.
They generally move in lines, which are about three feet from each
other, and exactly parallel, going directly forward through rivers and
lakes; and when they meet with stacks of hay or corn, gnawing their way
through them instead of passing round.[882] These excursions usually
precede a rigorous winter, of which the lemings seem in some way
forewarned.

[Illustration: Fig. 97.

The Leming, or Lapland Marmot (Mus Lemmus, Linn.)]

Vast troops of the wild ass, or _onager_ of the ancients, which inhabit
the mountainous deserts of Great Tartary, feed, during the summer, in
the tracts east and north of Lake Aral. In the autumn they collect in
herds of hundreds, and even thousands, and direct their course towards
Persia, to enjoy a warm retreat during winter.[883] Bands of two or
three hundred quaggas, a species of wild ass, are sometimes seen to
migrate from the tropical plains of southern Africa to the vicinity of
the Malaleveen River. During their migrations they are followed by
lions, who slaughter them night by night.[884]

The migratory swarms of the springbok, or Cape antelope, afford another
illustration of the rapidity with which a species under certain
circumstances may be diffused over a continent. When the stagnant pools
of the immense deserts south of the Orange River dry up, which often
happens after intervals of three or four years, myriads of these animals
desert the parched soil, and pour down like a deluge on the cultivated
regions near the Cape. The havoc committed by them resembles that of the
African locusts; and so crowded are the herds, that "the lion has been
seen to walk in the midst of the compressed phalanx with only as much
room between him and his victims as the fears of those immediately
around could procure by pressing outwards."[885]

[Illustration: Fig. 98.

Mydaus meliceps, or badger-headed Mydaus. Length, including the tail, 16
inches.]

Dr. Horsfield mentions a singular fact in regard to the geographical
distribution of the _Mydaus meliceps_, an animal intermediate between
the polecat and badger. It inhabits Java, and is "confined exclusively
to those mountains which have an elevation of more than seven thousand
feet above the level of the ocean; on these it occurs with the same
regularity as many plants. The long extended surface of Java, abounding
wit