Again,

some animals are supplied with blood, as man, the horse,
and all such animals as are, when full-grown, either destitute of
feet, or two-footed, or four-footed; other animals are bloodless, such
as the bee and the wasp, and, of marine animals, the cuttle-fish,
the crawfish, and all such animals as have more than four feet.
Again, some animals are viviparous, others oviparous, others
vermiparous or 'grub-bearing'. Some are viviparous, such as man, the
horse, the seal, and all other animals that are hair-coated, and, of
marine animals, the cetaceans, as the dolphin, and the so-called
Selachia. (Of these latter animals, some have a tubular air-passage
and no gills, as the dolphin and the whale: the dolphin with the
air-passage going through its back, the whale with the air-passage
in its forehead; others have uncovered gills, as the Selachia, the
sharks and rays.)