itude of Cape Comorin. It has long since been ascertained
that they frequent the seas that separate the islands of the Pacific;
but they have never yet been found in the Atlantic, nor even on the
western shores of tropical America. And if, as has been stated[1], they
have been seen on a late occasion in considerable numbers in the Bay of
Panama, the fact can only be regarded as one of the rare instances, in
which a change in the primary distribution of a race of animals has
occurred, either by an active or a passive immigration. Being
exclusively inhabitants of the sea, they are liable to be swept along by
the influence of currents; but to compensate for this they have been
endowed with a wonderful power of swimming. The individuals of all the
groups of terrestrial serpents are observed to be possessed of this
faculty to a greater or a less degree; and they can swim for a certain
distance without having any organs specially modified for the purpose;
except, perhaps, the lung, which is a long sac capable of taking in a
sufficient quantity of air, to keep the body of the snake above water.
Nor do we find any peculiar or specially adapted organs even in the
freshwater-snakes, although they can catch frogs or fishes while
swimming. But in the _hydrophids_, which are permanent inhabitants of
the ocean, and which in an adult state, approach the beach only
occasionally, and for very short times, the tail, which is rounded and
tapering in the others, is compressed into a vertical rudder-like organ,
similar to, and answering all the purposes of, the caudal fin in a fish.
When these snakes are brought on shore or on the deck of a ship, they
are helpless and struggle vainly in awkward attitudes. Their food
consists exclusively of such fishes as are found near the surface; a
fact which affords ample proof that they do not descend to great depths,
although they can dive as well as swim. They are often found in groups
during calm weather, sleeping on the sea; but owing to their extreme
caution and shyness, attempts to catch them are rarely successful; on
the least alarm, they suddenly expel the air from their lungs and
descend below the surface; a long stream of rising air-bubbles marking
the rapid course which they make below. Their poisonous nature has been
questioned; but the presence of a strong perforated tooth and of a
venomous gland sufficiently attest their dangerous powers, even if these
had not been demonstrated by the effect