The Seals, Walruses, Sea-Elephants and Sea-Lions, etc., are grouped in a
family known as the Amphibious Carnivora—or the flesh-eating animals
that live both on the land and in the water. Some Naturalists object to
this classification, and say that the word Amphibia should only be
applied to the Batrachians—like the Frogs and the Reptiles that can
breath either in the water by means of gills, or in the air by means of
lungs.
But this expression has been altered from its true meaning, and what are
now called Amphibia, are the animals like the Seals, etc., which are
organized for living in the water, but which can, with difficulty move
about on the land.
Very curious animals are found in the Seal family. Their bodies are long
and cylinder-shaped, with many of the characteristics of the Fishes; and
their limbs are converted into fins by being provided with broad
connecting webs. The fur of these various animals is composed of a
woolly compact coat, the thickness and fineness of which increases with
the severity of the climate they inhabit; and which is covered by rather
coarse hairs lubricated with oil, the object of which is to prevent the
water from penetrating to the skin. A thick layer of fat protects the
body against cold, especially in the species which inhabit the frigid
regions.
The Seal family live in numerous troops, and feed on Fishes, Mollusks,
Crustaceans, etc. They are famous divers, and although they must come to
the surface to breathe, they can remain a long time under water. This is
explained by a peculiarity in their circulation. They are provided with
reservoirs in which the blood accumulates while the lungs are inactive;
and the animal is not suffocated while under water, because suffocation
only comes from the stoppage of circulation as soon as the breathing is
suspended, and in this case the circulation continues all the time the
animal is under water; and it is only when the blood overruns these
reservoirs that it is necessary for them to return to the surface of the
water to breathe.
Owing to this precaution of nature the Amphibia can wander freely about
in the depths of the ocean in search of their food.
As their members are badly fitted for locomotion on land, the Amphibia
only leave the water when they want to sleep, or while their babies are
very young, and feed on the mother’s milk. But these clumsy little
fellows soon grow strong enough to dive to the bottom of the ocean with
their mother, and search for food among the small Fishes, etc.
The Amphibia do not live in very warm regions, and they increase more
and more in number in proportion as one advances towards the poles. They
are found on the coasts of Europe—in the North Seas, the British Channel
and the Mediterranean; and in southern latitudes of the Pacific, along
the coast of Southern Chili and upon the shores of New Zealand.