Thus the whole coast of our continent is peopled more or less thickly with animals. But now arises a new set of inquiries; how far into the sea do these animals extend? how wide is their domain? Do they wander at will in the ocean, or are they bound by any law to keep within a certain distance of the shore? These questions would seem to be easily answered, for wherever we go on the surface of the sea, and as far as the eye can penetrate into its depths, we find it full of life; and yet a closer examination shows that all these beings have their appointed boundaries. Along the shores, animal and vegetable life seems to be distributed in certain definite combinations. Those who are familiar with rocky beaches readily recognize the different bands of color produced by the various kinds of sea-weed growing at given distances between high and low-water-mark. First comes the olive green rockweed (the Fucus), and with it are found barnacles and small Crustacea, myriads of which are to be seen hopping about in this rockweed when the tide is out. Below these are the brown crispy Rhodersperms and Melanosperms, and associated with them are Star-fishes, Crabs, and Cockles. Next in order is the Laminarian zone. Here we have the broad fronds of the Laminaria, the "devil's aprons," as the fishermen call them; in this zone is the home of the Sea-urchin, and here will be found also a few small fishes. Lastly we have the Coralline zone, so called on account of the lime deposit in the sea-weeds, giving them the rigidity of corals; among these the Lobsters make their appearance, and here are to be found also numerous clusters of Hydroids, the nurses of the Jelly-fishes. This distribution is not casual; these belts of animal and vegetable life are sharply defined and so constantly associated, that they must be controlled by the same physical laws. The first important investigations on this subject were made by Örsted, the distinguished Danish naturalist. He undertook a complete topographical survey of the coast near which he lived, carrying his soundings to a depth of some twelve fathoms, and found that both the fauna and flora of the shore were divided, according to the depth of the water, into bands of vegetable and animal life, corresponding very nearly with those given above. His observations were, however, limited, not extending beyond the neighborhood of his home. It is to Edward Forbes, the great English naturalist, whose short life was so rich in results for science, that we owe a more complete and extensive investigation of the whole subject. [Illustration: Diagram of a rocky beach.]