5. The soft parts are either entirely so, or so long as they are in a natural condition, as blood, serum, fat, tallow, marrow, semen, gall, milk (in those animals which give milk), flesh, and other analogous parts of the body. In another manner also the excretions of the body belong to this class, as phlegm, and the excrements of the abdomen and bladder; the hard and dry parts are sinew, skin, vein, hair, bone, cartilage, nail, horn, for that part bears the same name, and on the whole is called horn, and the other parts of the body which are analogous to these. 6. Animals also differ in their manner of life, in their actions and dispositions, and in their parts. We will first of all speak generally of these differences, and afterwards consider each species separately. The following are the points in which they vary in manner of life, in their actions and dispositions. Some animals are aquatic, others live on the land; and the aquatic may again be divided into two classes, for some entirely exist and procure their food in the water, and take in and give out water, and cannot live without it; this is the nature of most fishes. But there are others which, though they live and feed in the water, do not take in water but air, and produce their young out of the water. Many of these animals are furnished with feet, as the otter and the latax[1] and the crocodile, or with wings, as the seagull and diver, and others are without feet, as the water-serpent. Some procure their food from the water, and cannot live out of the water, but neither inhale air nor water, as the acalephe[2] and the oyster. [1] Beaver, Castor fiber. [2] Medusa, or perhaps Actinia, or both. 7. Different aquatic animals are found in the sea, in rivers, in lakes, and in marshes, as the frog and newt, and of marine animals some are pelagic, some littoral, and some saxatile. Some land animals take in and give out air, and this is called inhaling and exhaling; such are man, and all other land animals which are furnished with lungs; some, however, which procure their food from the earth, do not inhale air, as the wasp, the bee, and all other insects.[3] By insects I mean those animals which have divisions in their bodies, whether in the lower part only, or both in the upper and lower. Many land animals, as I have already observed, procure their food from the water, but there are no aquatic or marine animals which find their food on land. There are some animals which at first inhabit the water, but afterwards change into a different form, and live out of the water; this happens to the gnat in the rivers, and ...[4] which afterwards becomes an œstrum.[5] [3] Under the class ἔντομα are probably included all annulose animals. [4] Some words appear to be lost in this place. [5] Tabanus, gad-fly.