The anemones deposit eggs in vast numbers, which change into strange, free-swimming animals that finally settle upon the bottom and soon grow into the adult forms. They have another method of developing. Singular little "buds" appear on the sides and base of the adult, which soon resemble the parent. The anemone is very long-lived; specimens have been kept for nearly a century. They also have a marvelous faculty for renewing themselves if injured. If one is divided, sometimes two anemones will be the result, recalling their distant cousin the little hydra, which when turned inside out receives its food and eats as though nothing had happened. No amount of mutilating appears to affect its various portions, as each soon develops into a perfect hydra.
The sea anemone is a common form of the aquarium. It is easily secured by those living near the ocean, forming a most interesting pet, taking food from the hand, and soon proving itself possessed of a remarkable appetite. The anemones are among the great purifiers of the ocean, devouring a vast amount of dead matter which might pollute the water, and continually pumping the water through their systems, sifting out the animal life, dead or alive. Aside from this, the anemones are chiefly useful as beautifiers of the ocean. In the Mediterranean Sea they are sometimes eaten by the Italians and French. Certain fishes and crustaceans prey upon them.
V. THE CORALS
The real gardens of the sea, the "Gulfs enchanted where the siren sings and coral reefs lie bare," are in the tropics, where the great coral reefs extend for miles in countless shapes, forming branches, heads, fans, and many forms which never fail to delight the eye of the observer. For many years I lived upon a coral key or island in the center of a coral reef. The key was half a mile in circuit, and was made up of coral sand, or sand composed of ground coral and shells. It was just above the surface, so near that almost anywhere salt water could be found a few feet below; yet in this sandy soil cocoanuts, bananas, and other tropical plants grew in profusion. A grove of bay cedars and mangroves added to its attractiveness and gave it the name of Garden Key.
Fig. 33.—Branch coral (reef builder), showing polyps expanded and withdrawn.
The history of this reef is easily told. Ages ago there was no reef. There was no island, but perhaps a submarine plateau, a long distance below the surface. It gradually grew by the dropping of the minute shells described on page 15. After many ages it attained an altitude which brought its summit within one hundred or two hundred feet of the surface. Now its growth became more rapid as a new factor came upon the scene. The reef-building corals do not, as a rule, thrive or grow in water deeper than two hundred feet, and nearly all prefer water very much shallower. So, as soon as the submarine hill entered this zone, the eggs and young of the various reef-building corals (Figs. 33, 37) obtained a foothold, and the growth was ever upward, countless forms aiding in it. The lower portion was continually dying, the animals occupying only the upper story, so that a cap of stone was being formed on the top of the hill which after many years reached the surface. The sea now broke up the tips of the branch coral. They became ground up. A curious seaweed which secreted lime appeared, and this and the ground coral and shells formed a muddy flat which, aided by various objects that float upon the ocean, constituted a miniature island. Now something which resembled a cigar, one end downward, came floating along. If we could have examined it, curious little rootlets would have been seen growing from the lower portion. This stranded on the island, and the little cigar proved to be the seed of the mangrove tree; its roots grew and caught in the mud, and soon a tree appeared growing on the new-born island. Its roots presented a base, about which sand and mud rapidly accumulated, and so the key or island grew until it became the Garden Key of to-day.
