In the coral formation, this chasm, even as to the ma rine strata, is filled up. Such is the nature of the animals in this case, that, instead of spreading their manufactures, (to use this word,) along the bottom of the ocean, as the shell-fish do, and concealing their stupendous works far beneath regions accessible to man, to be discovered only by the eventual geologists of future possible worlds; their tendency is to seek the surface of the sea. There the huge strata which they produce are brought to light, even during their own and our existence, and we become ac quainted with locks that may, at the same time, be consi dered as fossil and living also. When once the animals have deserted their habitations, when these have reached, as we shall immediately chew that they do, above the sur face of the water, and even far up into dry land, into isl ands of great extent, they must be considered as fossil productions, as much as any other calcareous strata, and are therefore proper objects of examination in this essay. There are few, at the same time, that arc more interesting, and we cannot fail, therefore, to gratify our readers with an account of these very singular productions, on which depend so many lands, and the existence and happiness of so large a mass of population as they present.
The corals themselves, as far as we can undertake to lescribe them, may be understood generally from the descriptions and figures which we have given ; but they are objects which, from their beauty and singularity, are well known even to those who have never paid any atten tion to natural history. We need not describe all the spe cies which are engaged in these operations, nor, indeed, are they all known, any more than the economy of each individual. It will be sufficient for our purpose to give a general notion of any one, as the general habits, forms, and actions of the whole are fundamentally the same, how ever the external appearance of their produce or habita tion may differ.
It appears that each coral, whatever it be, is a solid calcareous structure, some hat resembling a vegetable in the general progress and increase of its parts, inhabited by numerous similar animals, which are precisely the same for each individual coral, but different in the differ ent species. Each of these corals may thus be conceived to form a colony, and the inhabitants are disposed in mi nute cells, where they reside and carry on the operation of extending their habitations. In these operations, how ever independently each seems to act in the production of its own cell, or in the extension of its own immediate neighbourhood, the whole are regulated by some common mysterious principle, by which they all concur towards the production of a structure that would rather seem to have been directed by one mind. Now nothing very ana logous to this takes place in the animal creation, except in the case of the gregarious insects that form a common habitation for breeding ; such as the bees. and the ants.
In these there is a possibility of personal communication; and that there is such, is proved by the accurate researches of many naturalists. No such communication can take place among the coral animals, hecause each is fixed and rooted in its cell, of which it forms a part. It may be considered, indeed, that the whole of the colony are parts of the structure which they inhabit, just as flowers are of a plant. This analogy is very strongly confirmed by at tending to the genus Vorticella, a soft animal, incapable of constructing such a habitation as the coral animal, yet possessing some very striking analogies to it. The sim ple vorticella is independent, and swims at liberty ; not unaptly resembling, at the same time, a flower or a bud just expanded ; appearing to consist a body resembling the calyx, provided with tentacula, that are like to statnina or petals. But if we proceed from the simplest vorticella onwards, we find a species which is immovably fixed by a pedicle of animal fibre to the spot where it was produced, or, at least, only capable of floating freely through the water. In further progress, two are united in one stem, and, at length, there are found one or more species in which a single stem produces numerous ramifications, each of which is terminated by the calyx formed animal, or flower, if we may so call it. In this case each animal is partially independent, yet all depend on the whole, so that, were it not for the demonstration of its being of an animal nature, it might be esteemed a vegetable. In what way this mutual dependence and co-operation of many animals to produce a common structure is managed, we cannot conjecture ; but it might be did we not linow the independent and single vorticella, that the ra mous one was itself but one animal, and that the flowers, or single vorticellx, were only its parts. The whole de pendence presents a singular analogy to the vegetable identity, where all the leaves and flowers conspire to gether to produce and propagate the plant, so as almost to lead us to conclude that there was here a perfect gra dation from one department of nature to the other.
This explains the dependence of the coral colony, as far as one difficulty can explain another. The only differ ence consists in the hardness or softness of the habitation, or tree, if it may be so called. In the vorticella it is a soft animal matter ; in the coral it is bony, or stony. And here, also, even the corals present an analogy to those ve getables which, like the chary and the coralline, incrust themselves with calcareous earth, or the equisetum, which secretes a siliceous bark.