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.