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History of Animals   

sheltered, genial, and supplied with fresh water.
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.
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.
When the Euxine is 'purged' a substance called phycus is carried
into the Hellespont, and this substance is of a pale yellow colour.
Some writers aver that it is the flower of the phycus, from which
rouge is made; it comes at the beginning of summer. Oysters and the
small fish of these localities feed on this substance, and some of the
inhabitants of these maritime districts say that the purple murex
derives its peculiar colour from it.

Marsh-fishes and river-fishes conceive at the age of five months
as a general rule, and deposit their spawn towards the close of the
year without exception. And with these fishes, like as with the marine
fishes, the female does not void all her eggs at one time, nor the
male his sperm; but they are at all times more or less provided, the
female with eggs, and the male with sperm. The-carp spawns as the
seasons come round, five or six times, and follows in spawning the
rising of the greater constellations. The chalcis spawns three
times, and the other fishes once only in the year. They all spawn in
pools left by the overflowing of rivers, and near to reedy places in
marshes; as for instance the phoxinus or minnow and the perch.
The glanis or sheat-fish and the perch deposit their spawn in
one continuous string, like the frog; so continuous, in fact, is the
convoluted spawn of the perch that, by reason of its smoothness, the
fishermen in the marshes can unwind it off the reeds like threads
off a reel. The larger individuals of the sheat-fish spawn in deep
waters, some in water of a fathom's depth, the smaller in shallower
water, generally close to the roots of the willow or of some other
tree, or close to reeds or to moss. At times these fishes intertwine
with one another, a big with a little one, and bring into
juxtaposition the ducts-which some writers designate as navels-at
the point where they emit the generative products and discharge the
egg in the case of the female and the milt in the case of the male.
Such eggs as are besprinkled with the milt grow, in a day or
thereabouts, whiter and larger, and in a little while afterwards the
fish's eyes become visible for these organs in all fishes, as for that
matter in all other animals, are early conspicuous and seem
disproportionately big. But such eggs as the milt fails to touch
remain, as with marine fishes, useless and infertile. From the fertile
eggs, as the little fish grow, a kind of sheath detaches itself;

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