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.

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.

Oviparous fish as a rule spawn only once a year. The little
phycis or black goby is an exception, as it spawns twice; the male
of the black goby differs from the female as being blacker and
having larger scales.

Fishes then in general produce their young by copulation, and
lay their eggs; but the pipefish, as some call it, when the time of
parturition arrives, bursts in two, and the eggs escape out. For the
fish has a diaphysis or cloven growth under the belly and abdomen
(like the blind snakes), and, after it has spawned by the splitting of
this diaphysis, the sides of the split grow together again.

Fishes for the most part are divided into males and females, but
one is puzzled to account for the erythrinus and the channa, for
specimens of these species are never caught except in a condition of
pregnancy.

With such fish as pair, eggs are the result of copulation, but
such fish have them also without copulation; and this is shown in
the case of some river-fish, for the minnow has eggs when quite
small,-almost, one may say, as soon as it is born. These fishes shed
their eggs little by little, and, as is stated, the males swallow
the greater part of them, and some portion of them goes to waste in
the water; but such of the eggs as the female deposits on the spawning
beds are saved. If all the eggs were preserved, each species would
be infinite in number. The greater number of these eggs so deposited
are not productive, but only those over which the male sheds the
milt or sperm; for when the female has laid her eggs, the male follows
and sheds its sperm over them, and from all the eggs so besprinkled
young fishes proceed, while the rest are left to their fate.

The same phenomenon is observed in the case of molluscs also;
for in the case of the cuttlefish or sepia, after the female has
deposited her eggs, the male besprinkles them. It is highly probable
that a similar phenomenon takes place in regard to molluscs in
general, though up to the present time the phenomenon has been
observed only in the case of the cuttlefish.

Fishes deposit their eggs close in to shore, the goby close to
stones; and, by the way, the spawn of the goby is flat and crumbly.
Fish in general so deposit their eggs; for the water close in to shore
is warm and is better supplied with food than the outer sea, and
serves as a protection to the spawn against the voracity of the larger
fish. And it is for this reason that in the Euxine most fishes spawn
near the mouth of the river Thermodon, because the locality is
sheltered, genial, and supplied with fresh water.

Like the human
species it brings forth at all seasons of the year, but especially
at the time when the earliest kids are forthcoming. It conducts its
young ones, when they are about twelve days old, over and over again
during the day down to the sea, accustoming them by slow degrees to
the water. It slips down steep places instead of walking, from the
fact that it cannot steady itself by its feet. It can contract and
draw itself in, for it is fleshy and soft and its bones are gristly.
Owing to the flabbiness of its body it is difficult to kill a seal
by a blow, unless you strike it on the temple. It looks like a cow.
The female in regard to its genital organs resembles the female of the
ray; in all other respects it resembles the female of the human
species.

So much for the phenomena of generation and of parturition in
animals that live in water and are viviparous either internally or
externally.


Oviparous fishes have their womb bifurcate and placed low down, as
was said previously-and, by the way, all scaly fish are oviparous,
as the basse, the mullet, the grey mullet, and the etelis, and all the
so-called white-fish, and all the smooth or slippery fish except the
eel-and their roe is of a crumbling or granular substance. This
appearance is due to the fact that the whole womb of such fishes is
full of eggs, so that in little fishes there seem to be only a
couple of eggs there; for in small fishes the womb is
indistinguishable, from its diminutive size and thin contexture. The
pairing of fishes has been discussed previously.