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.

With regard to the crab, it has already been stated that it has
claws and feet, and their position has been set forth; furthermore,
for the most part they have the right claw bigger and stronger than
the left. It has also been stated' that in general the eyes of the
crab look sideways. Further, the trunk of the crab's body is single
and undivided, including its head and any other part it may possess.
Some crabs have eyes placed sideways on the upper part, immediately
under the back, and standing a long way apart, and some have their
eyes in the centre and close together, like the crabs of Heracleotis
and the so-called 'grannies'. The mouth lies underneath the eyes,
and inside it there are two teeth, as is the case with the crawfish,
only that in the crab the teeth are not rounded but long; and over the
teeth are two lids, and in betwixt them are structures such as the
crawfish has besides its teeth. The crab takes in water near by the
mouth, using the lids as a check to the inflow, and discharges the
water by two passages above the mouth, closing by means of the lids
the way by which it entered; and the two passage-ways are underneath
the eyes. When it has taken in water it closes its mouth by means of
both lids, and ejects the water in the way above described. Next after
the teeth comes the oesophagus, very short, so short in fact that
the stomach seems to come straightway after the mouth.