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.
All cartilaginous fishes have at one and the same time eggs
above close to the midriff (some larger, some smaller), in
considerable numbers, and also embryos lower down. And this
circumstance leads many to suppose that fishes of this species pair
and bear young every month, inasmuch as they do not produce all
their young at once, but now and again and over a lengthened period.
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