to some crevice or
overarching stone to await the returning vegetation of spring. So, in
the season of intense heat, the _Helix Waltoni_ of Ceylon, and others of
the same family, before retiring under cover, close the aperture of
their shells with an impervious epiphragm, which effectually protects
their moisture and juices from evaporation during the period of their
aestivation. The Bulimi of Chili have been found alive in England in a
box packed in cotton after an interval of two years, and the animal
inhabiting a land-shell from Suez, which was attached to a tablet and
deposited in the British Museum in 1846, was found in 1850 to have
formed a fresh epiphragm, and on being immersed in tepid water, it
emerged from its shell. It became torpid again on the 15th November,
1851, and was found dead and dried up in March, 1852.[1] But the
exceptions serve to prove the accuracy of Hunter's opinion almost as
strikingly as accordances, since the same genera of animals which
hybernate in Europe, where extreme cold disarranges their oeconomy,
evince no symptoms of lethargy in the tropics, provided their food be
not diminished by the heat. Ants, which are torpid in Europe during
winter, work all the year round in India, where sustenance is
uniform.[2] The Shrews of Ceylon (_Sorex montanus_ and _S. ferrugineus_
of Kelaart) which, like those at home, subsist upon insects, inhabit a
region where the equable temperature admits of the pursuit of their prey
at all seasons of the year; and hence, unlike those of Europe, they
never hybernate. A similar observation applies to the bats, which are
dormant during a northern winter when insects are rare, but never become
torpid in any part of the tropics.

[Footnote 1: _Annals of Natural History_, 1850. See Dr. BAIRD's _Account
of Helix desertorum; Excelsior, &c._, ch. i. p. 345.]

[Footnote 2: Colonel SYKES has described in the _Entomological Trans._
the operations of an ant which laid up a store of hay against the rainy
season.]

The bear, in like manner, is nowhere deprived of its activity except
when the rigour of severe frost cuts off its access to its accustomed
food. On the other hand, the tortoise, which immerses itself in
indurated mud during the hot months in Venezuela, shows no tendency to
torpor in Ceylon, where its food is permanent; and yet is subject to
hybernation when carried to the colder regions of Europe.

To the fish in the detached tanks and pools when the heat, by