h America, affords a curious illustration of this power. It is
altogether a highly singular creature, and has attracted a great deal of
notice because its organisation belongs to two types: it is, so to
speak, placed midway between the great classes of Reptiles and Fishes,
the characters which identify it with either being almost equally
balanced. Professor Owen and other eminent physiologists regard it as a
fish, while Professor Bischoff, with others equally learned, consider it
an Amphibian reptile.

It is the habits of this strange creature, however, which induce me to
notice it here. An inhabitant of rivers and ponds, which are swollen by
periodic rains, and subject to entire or partial desiccation by long
droughts, it is liable to be left by the retreating waters, exposed to
the burning sun, under which it would presently die, but for a special
provision.

The animal has the instinct to bury itself in the mud of the bottom, on
the approach of the droughts, penetrating to a depth of several feet.
There it coils itself into a ball, with the tail folded over the nose,
but so as to leave the nasal apertures uncovered; and, probably by its
wrigglings, it forms a cavity or chamber in the clay, which becomes
lined with a membranous slough thrown off from its body. Meanwhile the
water evaporates, the mud dries, bakes, and cracks under the torrid heat
of the dry season, thus allowing air to penetrate down to the retreat of
the torpid mud-fish, in sufficient quantity for its very sluggish
respiration. Here it lies inactive for five or six months, until the wet
season again sets in, and the returning floods cover the old beds,
soften the baked clay, revivify the imprisoned animal, and restore it to
liberty and aquatic locomotion.

To meet these strange conditions of life, the _Lepidosiren_ is furnished
with a twofold apparatus for respiration; the one aquatic, consisting
of gills, ordinarily contained in a branchial chamber, (but in one
species, at least, external,) suited for the separation of oxygen from
the water, and the other aerial, consisting of true lungs, closely
resembling those of serpents, though manifestly only a modification of
the well-known swim-bladder of many fishes,--by means of which the
animal breathes atmospheric air, during its periodic captivity.

The same emergency is met by other species in another way. It does not
appear that the _Lepidosiren_ has the power of voluntarily forsaking the
water, or