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.