in no instance to allow of the retraction of the head and limbs,—and the feet
are modified into perfect fin-lilce oars ; the toes being flat and far asunder, and
the whole of them enveloped in a continuous and undivided skin. These animals
are all marine, and generally vegetable feeders. One species, constituting
the genus Sphargis, is covered with a leathery skin, instead of the horny plates
which form the usual protection of the osseous shell.
Such is a brief, but necessary sketch of those characters of the principal
groups or families of the Testudinata, which appear to determine their habits
and modes of life. It will be obvious that so meagre a sketch can only be
intended to render intelligible, the account of their; natural history which
follows.
Whilst we see, in the other classes of the Yertebrata, the functions and enjoyments
of life provided for by the attributes of strength, of .fleetness, or of acute
powers of sensation; or, where these are wanting, by such a peculiar development
of the mental faculties, as shall equally avail their possessor in the fulfillment
of those destinies which appertain to him in the situation which he holds
in the scale of being; we turn, with a feeling of disappointment, to the sluggish,
torpid habits, and rude, ungainly structure which characterize most of the
Testudinata. But although these animals have not the power of escaping
from danger by swiftness of foot, they are provided, instead of such a means
of safety, with a hard solid case, impervious to the teeth even of beasts of prey;
a shelter more secure than the burrow of the marmot or the mole; Although
they cannot, like the migratory birds, wander from place to place, on the approach
of winter, in search of a more genial climate, yet their peculiar conformation
renders such a change unnecessary, by producing a greater or less
degree of torpor and insensibility as the cold advances, until every faculty and
function of life becomes extinct, and sensation itself is rendered less: and less
capable of suffering, exactly in proportion as the cause of pain and distress, in
the higher grades of animal life, increases, : It is not only in those animals
whose habits are most obviously interesting, that we are to look for illustrations
of the wisdom and power of the Creator, and of the universal adaptation
of the structure of animals to their habits: in this respect the tortoise and the
HISTORY A N D HABIT S OF THE TE STUDINATA. XXJ
toad are as perfect examples of creative wisdom, as the orang or the beaver,
the bee or the ant. But even amongst the Testudinata, the vital powers are
developed in very different degrees in the different forms. The Land Tortoises,
even in the tropical climates in which they most abound, and the temperature
of which is calculated to raise their sluggish powers to the greatest degree of
activity compatible with their organization, are still the awkward, slow-moving
beings to which so many opprobrious proverbs have been applied; and the
utmost extent of improvement of which they are susceptible, is an almost
ludicrous attempt at vivacity, which seems only to show how little external circumstances
can modify those habits which structure has limited and controlled.
But amongst some of the Fresh-water forms, the carnivorous habits by which
they are characterized require a rapidity and extent of movement widely different
from the contracted motions of the former group. Thus Chelydra serpentina,
the Snapping Turtle as it is commonly called, a native of the lakes and
rivers of South America, not only pursues its prey, which consists of fish and of
young water fowl, with great velocity and vigour, but seizes it with a rapid and
powerful movement of the neck, and a sudden snap of the jaws, sufficiently
forcible, as I have myself seen, to cut asunder a small stick. The movements,
indeed, of many of the fresh-water species, when pursuing their food, or
escaping from danger, are characterized by considerable speed and power.
The food of Tortoises varies according to their structure, and the situation
to which that structure adapts them. The land tortoises generally feed on
vegetable substances, preferring the succulent or milky plants of the natural
order Composites; such at least is the case with those which I have observed
in a state of comparative captivity. Thus the common tortoise of Europe,
Testudo grceca, usually selects the lettuce, the dandelion, the milk-thistle, and
other plants of this description: a specimen of Tpardalis, however, fed almost
exclusively on grass, which it plucked by a sidelong movement of the head.
On approaching a plant, the head is usually stretched out slowly towards it,
and its fitness for food evidently determined by the smell. The mouth is then
slowly opened, the head turned on one side- so as to take as large a portion of
the leaf as possible into the mouth, which is then closed, and the morsel cut
off between the horny edges of the upper and lower jaws, as if with shears.
f