Again, among the terrestrial animals, there are the serpents that are oviparous; of which, as yet, we have not spoken. These creatures couple by clasping each other, and entwine so closely around one another, that they might be taken for only one animal with two heads. The male viper thrusts[1] its head into the mouth of the female, which gnaws it in the transports of its passion. This, too, is the only one among the terrestrial animals that lays eggs within its body—of one colour, and soft, like those of fishes. On the third day it hatches its young in the uterus, and then excludes them, one every day, and generally twenty in number; the last ones become so impatient of their confinement, that they force a passage through the sides of their parent, and so kill her. Other serpents, again, lay eggs attached to one another, and then bury them in the earth; the young being hatched in the following year. Crocodiles sit on their eggs in turns, first the male, and then the female. But let us now turn to the generation of the rest of the terrestrial animals.