History of Animals
they have in common and of the parts peculiar to this genus or that,
and of the parts both composite and simple, whether without or within.
We now proceed to treat of animals devoid of blood. These animals
are divided into several genera.
One genus consists of so-called 'molluscs'; and by the term
'mollusc' we mean an animal that, being devoid of blood, has its
flesh-like substance outside, and any hard structure it may happen
to have, inside-in this respect resembling the red-blooded animals,
such as the genus of the cuttle-fish.
Another genus is that of the malacostraca. These are animals
that have their hard structure outside, and their soft or fleshlike
substance inside, and the hard substance belonging to them has to be
crushed rather than shattered; and to this genus belongs the
crawfish and the crab.
A third genus is that of the ostracoderms or 'testaceans'. These
are animals that have their hard substance outside and their
flesh-like substance within, and their hard substance can be shattered
but not crushed; and to this genus belong the snail and the oyster.
The fourth genus is that of insects; and this genus comprehends
numerous and dissimilar species. Insects are creatures that, as the
name implies, have nicks either on the belly or on the back, or on
both belly and back, and have no one part distinctly osseous and no
one part distinctly fleshy, but are throughout a something
intermediate between bone and flesh; that is to say, their body is
hard all through, inside and outside. Some insects are wingless,
such as the iulus and the centipede; some are winged, as the bee,
the cockchafer, and the wasp; and the same kind is in some cases
both winged and wingless, as the ant and the glow-worm.
In molluscs the external parts are as follows: in the first place,
the so-called feet; secondly, and attached to these, the head;
thirdly, the mantle-sac, containing the internal parts, and
incorrectly designated by some writers the head; and, fourthly, fins
round about the sac. (See diagram.) In all molluscs the head is found
to be between the feet and the belly. All molluscs are furnished with
eight feet, and in all cases these feet are severally furnished with
a double row of suckers, with the exception of one single species of
poulpe or octopus. The sepia, the small calamary and the large
calamary have an exceptional organ in a pair of long arms or
tentacles, having at their extremities a portion rendered rough by
the presence of two rows of suckers; and with these arms or tentacles
they apprehend their food and draw it into their mouths, and in
stormy weather they cling by them to a rock and sway about in the
rough water like ships lying at anchor. They swim by the aid of the
fins that they have about the sac. In all cases their feet are
furnished with suckers.
The octopus, by the way, uses his feelers either as feet or hands;
with the two which stand over his mouth he draws in food, and the last
of his feelers he employs in the act of copulation; and this last one,
by the way, is extremely sharp, is exceptional as being of a whitish
colour, and at its extremity is bifurcate; that is to say, it has an
additional something on the rachis, and by rachis is meant the
smooth surface or edge of the arm on the far side from the suckers.
In front of the sac and over the feelers they have a hollow
tube, by means of which they discharge any sea-water that they may
have taken into the sac of the body in the act of receiving food by
the mouth. They can shift the tube from side to side, and by means
of it they discharge the black liquid peculiar to the animal.
Stretching out its feet, it swims obliquely in the direction of
the so-called head, and by this mode of swimming it can see in
front, for its eyes are at the top, and in this attitude it has its
mouth at the rear. The 'head', while the creature is alive, is hard,
and looks as though it were inflated. It apprehends and retains
objects by means of the under-surface of its arms, and the membrane in