3. Of all animals the most remarkable in this particular is the dolphin, and some other aquatic animals and cetacea which are of this habit, as the whale and others which have a blowhole; for it is not easy to arrange them either with aquatic or terrestrial animals, if we consider animals that breathe air as terrestrial, and those that breathe water as aquatics, for they partake of the characters of both classes; for they receive the sea and eject it through their blowhole, and air through their lungs, for they have this part, and breathe through it. And the dolphin, when captured in nets, is often suffocated, from the impossibility of breathing. It will live for a long while out of water, snoring and groaning like other breathing animals. It sleeps with its snout above the water, in order that it may breathe through it. 4. It is thus impossible to arrange it under both of these contrary divisions, but it would appear that the aquatic animals must be further subdivided; for they breathe and eject water for the same reason as others breathe air, for the sake of coolness. Other animals do this for the sake of food; for those animals which obtain their food in the water, must also, at the same time, swallow some of the fluid, and have an organ by which they can eject it. Those creatures which use water instead of air for breathing have gills; those that use it for food have a blowhole. These creatures are sanguineous. The nature of the malacia and malacostraca is the same; for these swallow water for food. 5. Those animals which breathe air, but live in the water, and those which breathe water, and have gills, but go out upon dry land and take their food there, belong to two divisions of aquatic animals. This last division is represented by a single animal called the cordylus (water newt); for this animal has no lungs, but gills; and it goes on dry land to procure its food. It has four feet, so that it appears natural that it should walk. In all these animals nature appears to be, as it were, turned aside, and some of the males appear to be females, and the females have a male appearance; for animals which have but small diversity in particular parts, exhibit great variations in the whole body.