The shell-fish known as the oyster drill is one of the greatest of all enemies to young oysters, which he destroys by boring minute holes through their shells, and when the oyster opens, after death, eating him up. It is not known how he drills this very minute hole so quickly. The clinker (_serpula_) is really a vast marine tenement-house for a social community of beautiful sea-worms, who build up houses of shelly tubes twisted and fastened together. Each worm has a stopper, or cork, to his shell, with which he can close up the entrance to his house. When this sea-worm is feeding he throws out from the entrance of his tube a beautiful double plume. These worms are the favorite food of the sea-horse, who sucks them out with a sharp snapping noise. [Illustration: SEA-HORSE.] The sea-horse is considered to be one of the greatest prizes that can be obtained for an aquarium. For dignity of carriage, grace of motion, and beauty of form, he excels all other fish. The papa sea-horse takes care of his children the same as the pipe-fish, to which he is closely related; only his pocket is in front of him, and is much larger, and different in shape. This pocket is lined inside with a fatty substance, on which the young sea-horses feed till they are strong enough to be crowded into the world. The sea-horse, when he thinks it time to turn out his children, presses his big pocket (for he has no hands nor claws) against a shell or piece of stone, and out swim the young horses. At first they are apt to form into bundles by locking their tails together, but as they become accustomed to their new surroundings, and are stronger, they separate. The male sea-horse displays much pride over his young, and remains with them several days. Sea-horses can look two ways at once, as each eye moves independently of the other. [Illustration: TUBE-FLOWER AND SERPULA.] The tube-flower is very common along our coast. It lives in a long, thin, light-colored tube, composed of a material resembling horn. It has the power of stinging slightly, but, for all that, is so beautiful that no aquarium should be without it. This animal casts off its flower, or head, every few days, after which a new one makes its appearance. [Illustration: SEA-ANEMONE.]