3170. Upon the surface of the ramules or the leaves are apertures, out of which the mucous substance protrudes the radiated mouth. But these mouths are frequently, especially in the Cystic corallines, of two different modes of formation. The one kind are cysts without filaments, and contain ova, which are developed and fall out. The others have filaments, which move and do not produce ova. The former look like seed-capsules, the latter like flowers with stamina, while the entire trunk resembles a monœcious plant.
3171. With increased oxydation calcareous earth is deposited in the external tegument or rind, and the stem is converted into stone—Lithozoa, Lithophyta, Corals.
This calcareous earth contains the most general acid, or the carbonic, and thus oxygen combined with the inorganic carbon, while the bones contain phosphoric acid, oxydized gelatine.
3172. As the calcareous earth is, properly speaking, only a granular deposit in the tegument, like it is in the cartilages of the higher animals; so is it not to be regarded as a free worm-tube, but as the body itself. Meanwhile it forms a tube open above, from which the mouth of the animal projects.
3173. As the animal ramifies, so also do the stony tubes increase, and there originates a phytoidal or plant-like stem, but one consisting of a stony mass.
3174. Thus the Coral is the earth-animal, and indicates the globular or osseous mass under its first grade of formation in the animal kingdom.
But there are also Polyps, whose stem only originates through saccular inversion of the upper portion of the animal's body; yet this is only distinct in the soft stems. In most of the species, where a separate intestine is to be found, it is probably only the upper part of the body which is so inverted. Meanwhile there are some, whose intestine forms a circle by returning upon itself, and opens into an anus.
3175. If then the Infusoria are the vitellus or seed of the animal kingdom; in like manner the Corals are its ova. The carbonate of lime is the shell surrounding the albumen, while the animal or intestine is the vitellus—Albumen-animals.
3176. Nature forms these living ova, when she takes vitellus and albumen out of the sea-slime, invests them with a shell derived from the earth, and hatches them, after they have been vivified by sun and air.
Class 3. Absorbent, Involucral Animals.