CORALLINA, or CORAL, in zoology, a genus belonging to the order of vermes zoophyta. The trunk is radicated, jointed, and calcareous. The species are eight, distinguished by the form of their branches, and are found in the ocean adhering to stones, bones, shells, &c. The corals were formerly believed to be vegetable substances hardened by the air; but are now known to be composed of congeries of animals, which are even endowed with the faculty of moving spontaneously.

The islands in the South-sea are mostly coral rocks covered over with earth. The little creatures, which have scarce sensation enough to distinguish them from plants, build up a rocky structure from the bottom of that sea, too deep to be measured by human art, till it reaches the surface. Some of these coralline islands appear to be of a much older date than others; particularly the Friendly islands; and it is probable that as these submarine works are continually going on, new islands may by that means frequently be produced.

M. de Peyronnel of Marfeilles, in consequence of a series of experiments and observations from about the year 1720 to 1750, seems to have been the first who threw a proper light upon the nature and production of coral and similar marine substances. Those bodies, which the count de Marigny imagined to be flowers, this ingenious naturalist discovered to be insects inhabiting the coral; for upon taking branches of it out of the water, the flowers, which proceeded from a number of white points answering to the holes that pierced the bark, and the radiation of which resembled the flower of the olive-tree, entered into the bark and disappeared; but upon being again restored to the water, they were some hours after perceptible. These flowers spread on white paper lost their transparency, and became red as they dried. The holes in the bark correspond to small cavities upon the substance of the coral; and when the bark is removed, there may be seen an infinite quantity of little tubes connecting the bark with the inner substance, besides a great number of small glands adhering to them; and from these tubes Corallina and glands the milky juice of coral issues forth: the holes in the bark are the openings through which the insects that form these substances for their habitation come forth; and these cavities which are partly in the bark and partly in the substance, are the cells which they inhabit. The organs of the animal are contained in the tubes, and the glandules are the extremities of its feet, and the milky liquor is the blood and juice of the animal, which are more or less abundant in proportion to its health and vigour. When the insects are dead, they corrupt, and communicate to the water the smell of putrid fish. This juice or liquor runs along the furrows perceived upon the proper substance or body of coral, and stopping by little and little becomes fixed and hard, and is changed into stone; and being stopped in the bark, causes the coral to increase proportionably and in every direction. In forming coral, and other marine productions of this class, the animal labours like those of the tectaceous kind, each according to his species; and their productions vary according to their several forms, magnitudes, and colours.

The coral insect, or polype, M. Peyronnel observes, expands itself in water, and contracts itself in air, or when it is touched with the hand in water, or acid liquors are poured upon it: and he actually saw these insects move their claws or legs, and expand themselves, when the sea-water containing coral was placed near the fire, and keep them in their expanded state when separated from the coral in boiling water. Broken branches of coral have been observed to fasten themselves to other branches, and have continued to grow; and this is the case when they are connected with detached pieces of rock and other substances, from which no nourishment could be derived. The coral insects in their cells, not having been injured, continue their operations; and as they draw no nourishment from the stone of the coral, they are able to increase in a detached and separate state. Coral was found to be equally red in the sea as out of it; and it was more shining when just taken out of the water than even when it is polished; and the bark by being dried becomes somewhat pale. M. Peyronnel found that it grows in different directions, sometimes perpendicularly downwards, sometimes horizontally, and sometimes upwards; and in the caverns of the sea, open to every exposure.

This system was little regarded, though first communicated to the Academy of Sciences at Paris in 1727, till Mr Trembley's discovery of the fresh-water polype; but since that time, it has been confirmed by the observations of M. Bernard de Jussieu on the sea-coasts of Normandy, and those of M. de Reaumur near Rochelle. M. Donati of Turin has also adopted the same hypothesis, viz. that coral is a mass of animals of the polype kind; and instead of representing the polype beds and cells which they contain as the work of polypes, he thinks it more just to say, that coral and other coralline bodies have the same relation to the polypes united to them, that there is between the shell of a snail and the snail itself, or the bones of an animal and the animal itself.

The same system has also been excellently illustrated and established by Mr Ellis, in answer to the objections. There are properly but three kinds of coral; red, white, and black: the black is the rarest, and most esteemed; but the red was formerly used in medicine. It must be chosen thick, smooth, and shining, and of a beautiful red, not covered with any tartarous matter. However, this substance is now scarce ever prescribed by any intelligent practitioner.

When coral is newly taken up out of the sea, the small protuberances on its surface are soft, and yield, on being pressed, a milky juice which effervesces with acids. The cortical part with which the coral is all over covered is not near so compact as the internal, and may easily be taken off whilst fresh; and from this part it is usually freed before it comes to the market. The greatest coral trade is in Genoa and Leghorn. The small sprigs unfit for ornamental uses are in the shops levigated into a subtle powder; which, however, has no medicinal virtues superior to the common tincture. Coral is not unfrequently imitated by artificial compositions, some of which are made to resemble it exactly; but the abuse may be discovered by fire; the counterfeit not affording the alkaline earth which is afforded by the genuine coral. The colouring ingredients in the artificial coral are cinnamon and masticum, both of which are easily discovered. The natural coral seems to receive its colour from iron; for spirit of vitriol acquires from it a ferruginous taste; and on calcining the coral, some particles are found among the ashes that are attracted by the magnet. Sixteen ounces of coral, according to Neumann, when distilled in an open fire, yield about six scruples and an half of volatile alkaline spirit, with two or three grains of an empyreumatic oil; from the caput mortuum calcined, five scruples and a half of fixed salt may be extracted. In former times, many extraordinary virtues were expected from this substance, on account of its fine red colour; and therefore a great number of methods were tried to extract this colour by means of spirit of wine. None of these, however, succeeded. A red colour was indeed sometimes obtained, but it turned out the same whether any coral was used in the operation or not. In some of these processes, however, the coral loses its colour. One method of making the tincture is by dissolving a pound of sugar in a little water, and then adding half a pound of wax. A pound of coral boiled in this mixture loses its redness, but is found to be unaltered in other respects. In order to prepare the tincture, the wax and sugar must be dissolved in spirit of wine.