We shall commence, then, with testaceans, and then proceed to crustaceans, and then to the other genera in due order; and these other genera are molluscs, and insects, then fishes viviparous and fishes oviparous, and next birds; and afterwards we shall treat of animals provided with feet, both such as are oviparous and such as are viviparous; and we may observe that some quadrupeds are viviparous, but that the only viviparous biped is man.