The so-called smooth shark has its eggs in betwixt the wombs
like the dog-fish; these eggs shift into each of the two horns of
the womb and descend, and the young develop with the navel-string
attached to the womb, so that, as the egg-substance gets used up,
the embryo is sustained to all appearance just as in the case of
quadrupeds. The navel-string is long and adheres to the under part
of the womb (each navel-string being attached as it were by a sucker),
and also to the centre of the embryo in the place where the liver is
situated. If the embryo be cut open, even though it has the
egg-substance no longer, the food inside is egg-like in appearance.
Each embryo, as in the case of quadrupeds, is provided with a
chorion and separate membranes. When young the embryo has its head
upwards, but downwards when it gets strong and is completed in form.
Males are generated on the left-hand side of the womb, and females
on the right-hand side, and males and females on the same side
together. If the embryo be cut open, then, as with quadrupeds, such
internal organs as it is furnished with, as for instance the liver,
are found to be large and supplied with blood.