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. CHAP. 79. (54.)—THE FIRST PERSON THAT FORMED ARTIFICIAL OYSTER-BEDS.