The first tenants should be the hardy varieties of the Sea-Anemones, or _Actiniae_,--which are Polyps, of the class Radiata. The _Actinia mesembryanthemum_ is the common smooth anemone, abounding on the coast, and often to be found attached to stones on the beach. "When closed," says Mr. Hibbert, "it has much resemblance to a ripe strawberry, being of a deep chocolate color, dotted with small yellow spots. When expanded, a circle of bright blue beads or tubercles is seen within the central opening; and a number of coral-like fingers or tentacles unfold from the centre, and spread out on all sides." It remains expanded for many days together, if the water be kept pure; and, having little desire for locomotion, stays, generally, about where it is placed. It is a carnivorous creature, and seeks its food with its ever-searching tentacles, thus drawing in fishes and mollusks, but, most frequently, the minute Infusoria. Like other polyps, it may be cut in two, and each part becomes a new creature. It is a very pretty and hardy object in the aquarium. There are many varieties, some of which are very delicate, as the _Actinia anguicoma_, or Snaky-locked Anemone, and the pink and brown _Actinia bellis_, which so resembles a daisy. Others, as the _Actinia parasitica_, are obtainable only by deep-sea dredging; "and, as its name implies, it usually inhabits the shell of some defunct mollusk. And more curious still, in the same shell we usually find a pretty crab, who acts as porter to the anemone. He drags the shell about with him like a palanquin, on which sits enthroned a very bloated, but gayly-dressed potentate, destitute of power to move it for himself."[B] [Footnote B: Hibbert's _Book of the Aquarium_.] The _Actinia gemmacea_, or Gemmed Anemone, the _Actinia crassicornis_, and the Plumose Anemone are all beautiful, but tender varieties. The Anemones require but little care; they do not generally need feeding, though the Daisy and Plumose Anemone greedily take minced mutton, or oyster. But, as a rule, there are enough Infusoria for their subsistence; and it is safer not to feed them, as any fragments not consumed will decay, and contaminate the water. Next in order of usefulness, hardiness, and adaptability to the new aquarium, come the Mollusks. And of these, Snails and Periwinkles claim our respectful attention, as the most faithful, patient, and necessary scavengers of the confervoid growths, which soon obscure the marine aquarium.