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. At the same time they present a certain
resemblance to such of the animals we have described as the
Cephalopoda and Crustacea, inasmuch as they are free and unattached.
The same may also be said of the Testacea.
Such, then, is the structure of the parts that minister to nutrition
and which every animal must possess. But besides these organs it is
quite plain that in every animal there must be some part or other
which shall be analogous to what in sanguineous animals is the
presiding seat of sensation. Whether an animal has or has not blood,
it cannot possibly be without this. In the Cephalopoda this part
consists of a fluid substance contained in a membrane, through which
runs the gullet on its way to the stomach. It is attached to the
body rather towards its dorsal surface, and by some is called the
mytis. Just such another organ is found also in the Crustacea and
there too is known by the same name. This part is at once fluid and
corporeal and, as before said, is traversed by the gullet. For had the
gullet been placed between the mytis and the dorsal surface of the
animal, the hardness of the back would have interfered with its due
dilatation in the act of deglutition. On the outer surface of the
mytis runs the intestine; and in contact with this latter is placed
the ink-bag, so that it may be removed as far as possible from the
mouth and its obnoxious fluid be kept at a distance from the nobler
and sovereign part
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