in zoology, a genus belonging to the order of vermes mollusca. The body detached, naked, gibbous, terminated by the anus. Many tentacula at the other extremity, surrounding the mouth. There are nine species, all inhabitants of the ocean. The following descriptions of three species are given by Mr Barbut.

1. The tremula, or quivering holothuria, "commonly measures eight inches in length when dead; but alive it extends itself to more than a foot, or contracts its body into a ball. Its figure is cylindric, the diameter of which is every way equal to an inch and a few lines. The back of a dark brown prondly bears a variety of fleshy pyramid-like nipples, of a dark colour likewise at their basis, but white at their apex. They are observed to be of two different sizes; the larger occupy the length of the back, in number 14 on each side, at the distance of six lines one from the other, when the holothuria is contracted, but the intervening space is full eight lines when the animal is extended. Others like these are placed here and there profusely. The legs are scattered in like manner, without order, in every part of the back. Out of them all exudes a whitish mucilage serving to lubricate the body. Hence all the foreaid nipples seem to be so many glands furnished with an excretory duct, the aperture of which is so minute as not to be discoverable by the help of a common glass. That they are moreover provided with various muscles follows hence, that the holothuria can raise and obliterate them at pleasure. While the larger papillae are quite erect, their axis and the diameter of their base measures three lines. The belly or part opposite to the back in the holothuria is of a pale brown and set all over with cylindric tentacula, in such numbers that the head of a pin could scarce find room between. Their diameter is not much above a line, and their length is that of four lines. They are of a shining whiteness, except the extremity which is of a dark colour, and shaped like a socket. By the help of these tentacula the holothuria fixes its body at the bottom of the sea, so as not to be easily forced away by tempests, which would otherwise happen the more frequently, as this zoophyte dwells near the shores where the water fleese rises to a fathom's height. Now if it adheres to other bodies by means of its ventral tentacula, their point must necessarily have the form of a socket, as the cuttle-fish, sea-urchins, and star-fish have theirs shaped, by which they lay hold of any other body. From this situation of the holothuria at the bottom of the sea, which it also retains when kept in a vessel filled with sea-water, it must be evident to any one, that I have not groundlessly determined which was its back, and which its belly, which otherwise in a cylindric body would have been a difficult task. But as all animals uniformly walk or rest upon their bellies, and the holothuria has likewise that part of its body turned to the earth on which the cylindric tentacula are to be seen, it is clear that part is the abdomen or belly of this zoophyte. However, both the abdominal and dorsal tentacula are raised and obliterated at the animal's pleasure; from which it is no light conjecture to conclude, that they are furnished with elevating and depressing muscles, and particularly because all the foreaid tentacula disappear after the animal's death; and hence it farther appears, that all naturalists have given the representation of a dead holothuria, seeing they have assigned it no tentacula. I entertain some doubt whether the illustrious Linnæus himself did not draw his generical character of the holothuria from a dead subject, as he makes no mention of these tentacula."

2. The physalis, or bladder-shaped holothuria. The body of this species is oval, approaching to triangular, of a gloomy transparency; the back sharp edged, of a dark green colour, whence run out a number of finewes; anteriorly the body is of a reddish hue. The trunk spiral, reddish towards the thicker end. Many tentacula of unequal length under that thicker end; the shorter ones are taper and thicker, the middle ones capillary, the point clay colour and in shape like a ball; the rest which are longer are filiform, of which the middlemost is thicker and twice as long. Brown, in his Jamaica, calls it a diaphanous bladder with numerous tentacula representing a man's belly; above it is furnished with a comb full of cells; under the other extremity hang a number of branchy tentacula. It inhabits the seas.

3. The Pentaëtes, or five-rowed holothuria, has the mouth encompassed with tentacula, the body bearing tentacula five different ways. The animal is of a red colour, nearly oval, or somewhat cylindrical, assuming various shapes. The mouth is set round with ten rays brittle at the points. The body longitudinally dotted in five places with clay-coloured hollow warts, situate two together. It inhabits the sea of Norway, taking in and casting out again the water, as it either swims or dives to the bottom.