This growth is much more rapid than is generally supposed. The brain coral has been known to grow an inch or double its size in a year, and branch corals grow six or eight inches in this time. The corals and reefs form the great girders of the globe. The one off Australia is over a thousand miles in length, and all over the world are found fossil reefs. Thus in the Helderberg Mountains of New York I have followed and traced a coral reef, quite as wonderful in its way as that now growing and reaching out in Florida. By some upheaving of the earth's surface it has been pushed up into the air, a monument telling of the wonderful changes in nature and of the time when the waters of New York were as warm as those of Florida.
Fig. 40.—Surface of sea fan, enlarged.
Side by side with the corals and among the most beautiful objects of these submarine gardens, we find objects which resemble plumes and fans (Fig. 41). These are called Gorgonias, and are cousins of the corals. They resemble fans made up of a fine network or reticulated surface (Fig. 40). They are richly colored yellow, brown, and lavender, those of the latter color being particularly beautiful. When there is a surf they can be seen waving and bending gracefully, like the limbs of a tree in a gale. One of the best known of this group is the red coral of commerce, found in the Mediterranean Sea and the Indian Ocean. When alive, the coral base or branch is covered with a crust or skin in which the animals live, connected one with another. The polyp stands very high and is white. The crust itself, the solid lime base, is formed of a number of minute parallel tubes. This coral is dredged by collectors in the deep water and is scraped and polished until the beautiful red color, so highly prized for jewelry, is brought out.
Fig. 41.—Sea fan (Gorgonia).
Fig. 42.—Sea pen.
Closely allied to the corals are the sea pens (Fig. 42) which are common in almost all waters, and among the most beautiful forms. They are communities of polyps. In the sea pen the polyps are arranged along the branches so that a fluffy fan or an ostrich plume is imitated. I have taken these animals from deep water when they measured perhaps five inches in length; but an hour later when placed in a tank the insignificant animal had expanded until it was five times as large, and beautiful beyond description in its garb of delicate pink. At night it was a blaze of light which flashed from branch to branch, from polyp to polyp. When irritated in a perfectly dark room this specimen created so brilliant a phosphorescent light that I could almost read large print by it.
