4. The uterus of these fish, and of the other galeode, has a small appendage attached to the diaphragm like a white nipple, which is not present unless they are pregnant. The scylia and the batis have a shell-like substance, which contains the fluid of the ovum. In form the shell resembles the tongue of a wind instrument, and hair-like passages are attached to the shells. The young of the scylia, which some persons call nebria galei, are born when the shell falls off and bursts. The young of the batis when they are brought forth are excluded by the rupture of the shell. In the acantheas[203] galeos the ova are attached to the diaphragm above the nipples; and when the ovum descends, the young is attached to it after it is set free. The reproduction of the alopex is in the same manner. [203] Squalus Acanthias. 5. Most galei which are called smooth have the ova placed between the divisions of the uterus, like those of the scylia; and as they surround it, they descend into each division of the uterus, and they are produced, attached to the uterus by an umbilical cord; so that when the ova are taken out, they appear similar to the embryo of quadrupeds. And the long umbilical cord is attached to the lower part of the uterus, each part, as it were, attached to an acetabulum; and to the middle of the embryo near the liver. And when it is dissected, the food is like an egg, though the ovum be no longer there. There is a chorion, and peculiar membranes surrounding each of the embryos, as in quadrupeds. 6. The head of the embryo when it is just produced, is upwards; but as it grows and reaches maturity, it is placed downwards. The males are placed on the left, and the females on the right, or there are males and females together on the same side. The embryo, when dissected, resembles that of quadrupeds, in having its viscera such as it has, as the liver, large, and full of blood. In all the selache the ova are placed high up, near the diaphragm; many larger, and many smaller: and the embryos are placed below, wherefore it is probable that such fish produce their young, and copulate frequently during the same month, for they do not produce all their young at once, but frequently, and for a long while; but those that are in the lower part of the uterus are matured and brought to perfection. 7. The other galei both emit and receive their young into themselves, and so do the rhine and the narca; and a large narca has been observed to contain eighty young in herself. The acanthias is the only one of the galei which does not admit its young into itself, on account of their thorns. Among the flat fish the trygon and batos do not admit their young, on account of the roughness of the tail. Neither does the batrachus admit its young, on account of the size of their heads, and their thorns; and this is the only one that is not viviparous, as I previously observed. These are their mutual differences, and the manner of the development of their ova.