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History of Animals   

All crustaceans take in water close by the mouth. The crab
discharges it, closing up, as it does so, a small portion of the same,
and the crawfish discharges it by way of the gills; and, by the way,
the gill-shaped organs in the crawfish are very numerous.
The following properties are common to all crustaceans: they
have in all cases two teeth, or mandibles (for the front teeth in
the crawfish are two in number), and in all cases there is in the
mouth a small fleshy structure serving for a tongue; and the stomach
is close to the mouth, only that the crawfish has a little
oesophagus in front of the stomach, and there is a straight gut
attached to it. This gut, in the crawfish and its congeners, and in
the carids, extends in a straight line to the tail, and terminates
where the animal discharges the residuum, and where the female
deposits her spawn; in the crab it terminates where the flap is
situated, and in the centre of the flap. (And by the way, in all these
animals the spawn is deposited outside.) Further, the female has the
place for the spawn running along the gut. And, again, all these
animals have, more or less, an organ termed the 'mytis', or
We must now proceed to review their several differentiae.
The crawfish then, as has been said, has two teeth, large and
hollow, in which is contained a juice resembling the mytis, and in
between the teeth is a fleshy substance, shaped like a tongue. After
the mouth comes a short oesophagus, and then a membranous stomach
attached to the oesophagus, and at the orifice Of the stomach are
three teeth, two facing one another and a third standing by itself
underneath. Coming off at a bend from the stomach is a gut, simple and
of equal thickness throughout the entire length of the body until it
reaches the anal vent.
These are all common properties of the crawfish, the carid, and
the crab; for the crab, be it remembered, has two teeth.
Again, the crawfish has a duct attached all the way from the chest
to the anal vent; and this duct is connected with the ovary in the
female, and with the seminal ducts in the male. This passage is
attached to the concave surface of the flesh in such a way that the
flesh is in betwixt the duct and the gut; for the gut is related to
the convexity and this duct to the concavity, pretty much as is
observed in quadrupeds. And the duct is identical in both the sexes;
that is to say, the duct in both is thin and white, and charged with a
sallow-coloured moisture, and is attached to the chest.
(The following are the properties of the egg and of the convolutes
in the carid.)
The male, by the way, differs from the female in regard to its
flesh, in having in connexion with the chest two separate and distinct
white substances, resembling in colour and conformation the
tentacles of the cuttle-fish, and they are convoluted like the 'poppy'
or quasi-liver of the trumpet-shell. These organs have their
starting-point in 'cotyledons' or papillae, which are situated under
the hindmost feet; and hereabouts the flesh is red and blood-coloured,
but is slippery to the touch and in so far unlike flesh. Off from
the convolute organ at the chest branches off another coil about as
thick as ordinary twine; and underneath there are two granular seminal
bodies in juxta-position with the gut. These are the organs of the
male. The female has red-coloured eggs, which are adjacent to the
stomach and to each side of the gut all along to the fleshy parts,
being enveloped in a thin membrane.
Such are the parts, internal and external, of the carid.

The inner organs of sanguineous animals happen to have specific
designations; for these animals have in all cases the inner viscera,
but this is not the case with the bloodless animals, but what they
have in common with red-blooded animals is the stomach, the
oesophagus, and the gut.

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