CORALLINES.
"As for your pretty little seed-cups or vases, they are a sweet confirmation of the pleasure Nature seems to take in superadding elegance of form to most of her works. How poor and bungling are all the imitations of art! When I have the pleasure of seeing you next, we shall sit down—nay, kneel down—and admire these things."—Hogarth to Ellis.
The Alcyonaria are so designated from their principal type, that of the Alcyons. The fresh-water species are composed of a fleshy, sponge-like mass, consisting of vertical, aggregated, membranaceous tubes, which are open on the surface. In these tubes the polyps, which are Isidians, are located. The mouth is encircled with a single series of filiform tentacula, which, like those of the whole family, are depressed or incomplete on one side. The eggs are contained in the tubes, and are coriaceous and smooth. The tentacula of these polyps are generally eight, disposed somewhat like the barbs of a feather, and toothed on their edges like a saw, which has procured them the name of Ctenoceros, from the Greek word χτεις, a comb. Their bodies present eight perigastric lamellæ; their coral is often formed of spiculæ. We shall see, farther on, that among the Gorgonidæ the coral ceases to be parenchymous—that is, spongy and cellular; that its axis assumes a horny and resistant consistence, which becomes stony in the corallines. In this last group, the external bed, which is the special lodging of the polyps, always remains soft on the surface. We shall have a general idea of the organization, manners, and mode of multiplication among the Alcyonaria when we come to treat of corals and their strange history. The class Alcyonaria is divided into many orders. We shall consider—I. The Tubiporinæ. II. The Gorgoniadæ. III. The Pennatulidæ. IV. The Alcyonaria, properly so called.
I. THE TUBIPORINÆ
form a group consisting of several species, which live in the bosom of tropical seas, in which the Coral Islands form so prominent a feature. The group is exclusively formed of the curious genus Tubipora.
Fig. 41. Tubipora musica (Linn.), half the natural size.
The Tubipora is a calcareous coral, formed by a combination of distinct, regularly-arranged tubes, connected together at regulated distances by lamellar expansion of the same material. The aggregate formation resulting from this combination of tubes constitutes a rounded mass, which often attains a very considerable size. In Fig. 41 we have a representation of the zoophyte Tubipora musica and its product, which is sometimes designated by the vulgar name of Sea-Organ. In the engraving, 1 is the calcareous product, reduced to half its size; 2, is a portion in its natural size; 3, the tubes magnified, and containing the polyp which occupies the summit of the tube, the whole of which constitutes this curious coral; 4, is the polyp magnified; 5, the head or collection of tentacula of the individual polyp.