2. In all those that resemble the selache, the female is larger than the male; and in nearly all fish the female is larger than the male. The selache are those which have been mentioned; and the bos, lamia, æetus, narce, batrachus, and all the galeode. All the selache have been frequently observed to conduct themselves in this way. In all viviparous creatures the act occupies a longer time than in the oviparous. The dolphin and the cetacea also perform the act in the same manner, for the male attaches himself to the female for neither a very long, nor a very short time. 3. The males of some of the fish which resemble the selache differ from the females, in having two appendages near the anus, which the females have not, as in the galeodea; for these appendages exist in them all. Neither fish nor any other apodal animal has testicles, but the males, both of serpents and of fish, have two passages, which become full of a seminal fluid at the season of coition; and all of them project a milky fluid. These passages unite in one, as they do in birds; for birds have two internal testes, and so have all oviparous animals with feet. In the act of coition this single passage passes to, and is extended upon the pudendum and receptacle of the female. 4. In viviparous animals with feet, the external passage for the semen and the fluid excrement is the same: internally these passages are distinct, as I said before in describing the distinctive parts of animals. In animals which have no bladder, the anus is externally united with the passage of the semen, internally the passages are close together; and this is the same in both sexes: for none of them have a bladder, except the tortoise. The female of this animal, though furnished with a bladder, has but one passage; but the tortoise is oviparous. 5. The sexual intercourse of the oviparous fish is less evident, wherefore many persons suppose that the female is impregnated by swallowing the semen of the male; and they have been frequently observed to do this. This is seen at the season of coition, when the females follow the males, and are observed to strike them on the abdomen with their mouths, this causes the males to eject their semen more rapidly. The males do the same with the ova of the females, for they swallow them as they are extruded, and the fish are born from those ova which remain. 6. In Phœnicia they use each sex for capturing the other; for having taken the male cestreus, they entice the females with it, and so enclose them in a net. They use the females in the same way for catching the males. The frequent observation of these circumstances appears to corroborate this manner of intercourse among them. Quadrupeds also do the same thing, for at the season of coition both sexes emit a fluid, and smell to each other's pudenda.