The navel-string is attached a little way below the aperture
of the belly. When the creatures are young the navel-string is long,
but as they grow it diminishes in size; at length it gets small and
becomes incorporated, as was described in the case of birds. The
embryo and the egg are enveloped by a common membrane, and just
under this is another membrane that envelops the embryo by itself; and
in between the two membranes is a liquid. The food inside the
stomach of the little fishes resembles that inside the stomach of
young chicks, and is partly white and partly yellow.
As regards the shape of the womb, the reader is referred to my
treatise on Anatomy. The womb, however, is diverse in diverse
fishes, as for instance in the sharks as compared one with another
or as compared with the skate. That is to say, in some sharks the eggs
adhere in the middle of the womb round about the backbone, as has been
stated, and this is the case with the dog-fish; as the eggs grow
they shift their place; and since the womb is bifurcate and adheres to
the midriff, as in the rest of similar creatures, the eggs pass into
one or other of the two compartments.
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