Among _Polypi_, the higher forms, such as _Actiniæ_, are more abundant in shallow water than the lower coral-forming types. Among _Medusæ_, the young are either attached to the bottom, or grow from the depth, while the perfect free forms of these animals come to the surface. Among _Echinoderms_, the _Crinoids_ are deep-water forms; free star-fishes and _Echini_, and, above all _Holothuriæ_, living nearer the surface. Among _Mollusca_, the _Acephala_, which are lowest, have their lower types,--the _Brachiopods_, entirely confined to deep waters; the _Monomyarians_ appear next, and, above them, the _Dimyarians_; among these latter, the highest family, the _Nayades_, rises above the level of the ocean into the fresh waters, and extends even to considerable heights above the sea, in lakes and rivers. A number of examples of all classes should be mentioned, to shew that this is the universal case; as, for instance, among _Crustacea_ the _Macrura_ are, in general species of deeper water than the true crabs, of which some come even upon dry land. Again, on the slopes of our mountains, the highest forms among _Mammalia_ which remain numerous are the _Ruminants_ and _Rodents_. There are no _Carnivora_ living in high regions. Among birds of prey, we have the vultures, rising above the highest summits of mountains, while eagles and falcons hover over the woods and plains, by the water sides, and along the sea-shores. Among reptiles, salamanders, frogs, and toads occur higher than any turtles, lizards, &c. But the same adaptation may be traced with reference to the latitudes under which animals are found. Those of the higher latitudes, the arctic and antarctic species, resemble both the animals of high, prominent mountain chains, and those of the deep sea-waters, which there meet in the most unexpected combinations (and it is surprising to see how extensively this is the case); while, in lower latitudes, towards the tropics, we find everywhere the higher representatives of the same families. For instance, among _Mammalia_ we observe monkeys only in warm latitudes, and they die out in the warmer parts of the temperate zone. The great development of _Digitigrades_--lions, tigers, &c., takes place within the tropics, smaller species, like wolves and foxes, weasels, &c., occurring in the north, whilst the _Plantigrades_, which come nearer and nearer to the seal, follow an inverse progression, the largest and most powerful of them being the arctic ice bear, which meets there his family relations, the _Pinnipedia_, that are so numerous in the polar regions. Again, the families of _Ruminants_ and _Pachyderms_ seem to form an exception, for though belonging to the lower types of _Mammalia_, they prevail in the tropical zone; but let us remember that they were among the earlier inhabitants of our globe, and the fact of their occurring more extensively in warm climates is rather a reminiscence of the plan of creation in older times, than an