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. The
details, however, of these differences must be looked for in the
Researches concerning Animals and the treatises on Anatomy. For
while there are some points which can be made clear by verbal
description, there are others which are more suited for ocular
demonstration.
Peculiar among the Testacea are the sea-urchins and the animals
known as Tethya (Ascidians). The sea-urchins have five teeth, and in
the centre of these the fleshy body which is common to all the animals
we have been discussing. Immediately after this comes a gullet, and
then the stomach, divided into a number of separate compartments,
which look like so many distinct stomachs; for the cavities are
separate and all contain abundant residual matter. They are all,
however, connected with one and the same oesophagus, and they all
end in one and the same excremental vent. There is nothing besides the
stomach of a fleshy character, as has already been stated. All that
can be seen are the so-called ova, of which there are several,
contained each in a separate membrane, and certain black bodies
which have no name, and which, beginning at the animal's mouth, are
scattered round its body here and there promiscuously. These
sea-urchins are not all of one species, but there are several
different kinds, and in all of them the parts mentioned are to be
found. It is not, however, in every kind that the so-called ova are
edible
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