Those fish, again, which are covered with a stony coat, such as the oyster, are produced from mud in a putrid state, or else from the foam that has collected around ships which have been lying for a long time in the same position, about posts driven into the earth, and more especially around logs of wood.[2783] It has been discovered, of late years, in the oyster-beds,[2784] that the animal discharges an impregnating liquid,[2785] which has the appearance of milk. Eels, again, rub themselves against rocks, upon which, the particles[2786] which they thus scrape from off their bodies come to life, such being their only means of reproduction. The various kinds of fishes do not couple out of their own kind, with the exception of the squatina and the ray.[2787] The fish that is produced from the union of these two, resembles a ray in the fore part, and bears a name among the Greeks compounded of the two.[2788]
Certain animals are produced only at certain seasons of the year, both in water and on the land, such, for instance, as scallops, snails, and leeches, in the spring, which also disappear at stated periods. Among fishes, the wolf-fish[2789] and the trichias[2790] bring forth twice in the year, as also do all kinds of rock-fish; the mullet and the chalcis[2791] thrice in the year, the cyprinus[2792] six times, the scorpæna[2793] twice, and the sargus in spring and autumn. Among the flat-fish, the squatina brings forth twice a year, being the only[2794] one that does so at the setting of the[2795] Vergiliæ in autumn. Most fish spawn in the three months of April, May, and June. The salpa brings forth in the autumn, the sargus, the torpedo, and the squalus[2796] about the time of the autumnal equinox. The soft fishes[2797] bring forth in spring, the sæpia every month in the year; its eggs adhere together with a kind of black glutinous substance, in appearance like a bunch of grapes, and the male is very careful to go among them and breathe[2798] upon them, as otherwise they would be barren. The polypi couple in winter, and produce eggs in the spring twisted in spiral clusters, in a similar manner to the tendrils of the vine; and so remarkably prolific are they, that when the animal is killed in a state of pregnancy, the cavities of the head are quite unable to contain the multitude[2799] of eggs enclosed therein. They bring forth these eggs at the fiftieth day, but in consequence of the vast number of them, great multitudes perish. Cray-fish, and other sea-animals with a thinner crust, lay their eggs one upon the other, and then sit upon them. The female polypus sometimes sits upon its eggs, and at other times closes the entrance of its retreat by spreading out its feelers, interlaced like a net. The sæpia brings forth on dry land, among reeds or such sea-weed as it may find growing there, and hatches its eggs on the fifteenth day. The loligo produces its eggs out at sea, clustered together like those of the sæpia. The purple,[2800] the murex, and other fishes of the same kind, bring forth in the spring. Sea-urchins have their eggs at full moon during the winter; sea-snails[2801] also are produced during the winter season.
CHAP. 75.—FISHES WHICH ARE BOTH OVIPAROUS AND VIVIPAROUS.
The torpedo is known to have as many as eighty young ones. It produces within itself[2802] very soft eggs, which it then transfers to another place in the uterus, and from that part ejects them. The same is the case with all those fish to which we have given the name of cartilaginous; hence it is, that these alone of all the fishes are at once viviparous and oviparous. The male silurus[2803] is the only fish among them all that watches the eggs after they are brought forth, often for as long a period as fifty days, that they may not be devoured by other fish. The females of other kinds bring forth their eggs in the course of three days, if the male has only touched them.
CHAP. 76.—FISHES THE BELLY OF WHICH OPENS IN SPAWNING, AND THEN CLOSES AGAIN.
The sea-needle,[2804] or the belone, is the only fish in which the multitude of its eggs, in spawning, causes the belly to open asunder; but immediately after it has brought forth, the wound heals again: a thing which, it is said, is the case with the blind-worm as well. The sea-mouse[2805] digs a hole in the earth, deposits its eggs there, and then covers them up. On the thirtieth day it opens the hole, and leads its young to the water.
CHAP. 77. (52.)—FISHES WHICH HAVE A WOMB; THOSE WHICH IMPREGNATE THEMSELVES.
The fishes called the erythinus[2806] and the channe[2807] are said to have a womb; and those which by the Greeks are called trochi,[2808] it is said, impregnate themselves. The young of all aquatic animals are without sight at their birth.[2809]
CHAP. 78. (53.)—THE LONGEST LIVES KNOWN AMONGST FISHES.
We have lately heard of a remarkable instance of length of life in fish. Pausilypum[2810] is the name of a villa in Campania, not far from Neapolis; here, as we learn from the works of M. Annæus Seneca, a fish is known to have died sixty years after it had been placed in the preserves of Cæsar[2811] by Vedius Pollio; while others of the same kind, and its equals in age, were living at the time that he wrote. This mention of fish-preserves reminds me that I ought to mention a few more particulars connected with this subject, before we leave the aquatic animals.