“There’s nothing new under the sun.” This much quoted aphorism was forcibly suggested to our minds the other day while collecting specimens for our aquarium. In the first instance, a spider-crab, which, when stranded high and dry, appeared but an unsightly mass of tangled seaweed, when placed in the aquarium assumed all the beauties of a verdant grove. From every available point on the upper surface of his mossy-covered shell beautiful variegated plants streamed and waved their delicately-feathered fronds. Conspicuous amongst this luxurious growth were specimens of the corallines or sea-firs, which a casual observer might easily suppose to be miniature fir trees, but which in reality are plants only in semblance. Each of these delicate looking plants is actually an animal; in fact, a colony of animals. Closely placed along each side of the stem and delicate branches of other growths are slight projections or nodules, each containing a separate animal, which it surprises one to learn is eventually destined to become a jelly fish. The benefits of this partnership between crab and coralline is probably mutual, but the advantage to the crab in being thus arrayed is easily seen, as he can remain completely concealed from his enemies, and be able to stalk his prey with greater certainty of success. Shakespeare, in his tragedy of “Macbeth,” caused an attacking force to advance under cover of a wood they had cut down for that purpose, but here in Nature’s own arena similar tactics are being pursued, and probably were ages before “Birnam Wood came to Dunsinane,” or any of the _genus homo_ ever saw the light.