Development from the egg takes place similarly with fishes that
are oviparous internally and with fishes that are oviparous
externally; that is to say, the embryo comes at the upper end of the
egg and is enveloped in a membrane, and the eyes, large and spherical,
are the first organs visible. From this circumstance it is plain
that the assertion is untenable which is made by some writers, to wit,
that the young of oviparous fishes are generated like the grubs of
worms; for the opposite phenomena are observed in the case of these
grubs, in that their lower extremities are the larger at the outset,
and that the eyes and the head appear later on. After the egg has been
used up, the young fishes are like tadpoles in shape, and at first,
without taking any nutriment, they grow by sustenance derived from the
juice oozing from the egg; by and by, they are nourished up to full
growth by the river-waters.