the Mussel, in ichthyology; a genus of animals, belonging to the order of vermes testacea. The animal is an ascidia; the shell bivalve; often affixed to some substance by a beard; the hinge without a tooth, marked by a longitudinal hollow line. Of these animals there are a great many species, some of them inhabiting the seas, others the rivers and ponds. Several of them are remarkable for the beauty of their internal shell, and for the pearls which are sometimes found in them.

1. The edulis, or edible mussel, has a strong shell, slightly incurved on one side, and angulated on the other. other. The end near the hinge is pointed; the other rounded. When the epidermis is taken off, it is of a deep blue colour. It is found in immense beds, both in deep water and above low-water mark. The finest mussels in Britain are those called Hambleton hookers, from a village called Hambleton in that county. They are taken out of the sea, and placed in the river Wier, within reach of the tide, where they grow very fat and delicious. This species inhabits the European and Indian seas. Between the tropics it is largest, and smallest within the polar circle. It is said to be hurtful if too often eaten, or in too great quantities; and is even sometimes poisonous.

2. The modiolus, or great mussel, with a strong shell, blunted at the upper end; one side angulated near the middle; from thence dilating towards the end, which is rounded. It dwells in the Mediterranean, Indian, European, and American seas; and its flesh, which is a deep orange colour, is eatable. It is the greatest of the mussels known in Britain; being from six to seven inches in length; it lies at great depths; often seizes the baits of ground-lines, and is taken up with the hooks.

3. The cygnus, or swan mussel, with a thin brittle shell, very broad and convex, marked with concentric striae; attenuated towards one end, dilated towards the other; decorticated about the hinge; the colour a dull green; the length six inches, breadth three and a half. It is an inhabitant of the European rivers, frequenting chiefly their mouths.

4. The anatinus, or duck mussel, has a shell more oblong and less convex than the last; is very brittle and semitransparent; the space round the hinges like the last; the length about five inches, breadth two. It is found in Europe in fresh waters. Both it and the cygnus are devoured by swans and ducks; whence their names: crows also feed on these mussels, as well as on different other shell fish; and it is diverting to observe, that when the shell is too hard for their bills, they fly with it to a great height, drop the shell on a rock, and pick out the meat when the shell is fractured by the fall.

5. The cryphagalli, or cock's-comb mussel, has the shell folded or plicated as it were, spiny, and both lips rugged. It makes its abode in the coral beds of the Indian ocean.

6. The margaritiferus, or pearl-bearing mussel, has the shell compressed and flat, nearly orbicular, the base transverse, and imbricated with dentate coats. It dwells in the ocean of either India. This is the mater perlariae of Rumphius, or mother-of-pearl shell. On the inside it is exquisitely polished, and of the whitestens and water of pearl itself. It has also the Mytilus fame lustre on the outside after the external laminae have been taken off by aquafortis and the lapidary's mill. Mother-of-pearl is used in inlaid works, and in several toys, as snuff-boxes, &c.

7. The lithophagus, or stone-eating mussel, has the shell cylindric, the extremities both ways being rounded. It inhabits the Indian, European, and Mediterranean seas, penetrating and eating away marbles, corals, &c. The Indian shell is softer and nearly tough like leather, but the European is more brittle.

8. The violacea, or violet mussel, has the shell longitudinally furrowed, the rim very obtuse, somewhat formed like the mytilus edulis, but considerably larger and more flattened, of a beautiful violet colour. Inhabits the southern ocean. There are about 50 other species.

Mussels not only open and shut their shells at pleasure, but they have also a progressive motion; they can fasten themselves where they please; they retire water like the fishes; and some even flutter about on its surface so as to inhale air. If they lie in shallow places, a small circular motion is seen above the heel of the shell; and a few moments after, they cast out the water by one single stroke at the other end of the shell. The mouth is situated near the sharp angle of the animal, and is furnished with four floating fringes in the shape of multichios, which may perhaps answer the purpose of lips. The barbs which surround the edge of almost half the mussel, are a wonderful web of hollow fibres which serve as fins or organs of respiration, as vessels for the circulation of the fluids, and probably, as some philosophers suppose, as wedges for opening their shells; for we observe two large muscles or tendons for the purpose of shutting them; but we in vain look for their antagonists, or those which are destined to open them. When the mussel wishes to open itself, it relaxes the two muscles or tendons, and swells the fringes, which act as wedges and separate the shells. The animal shuts up itself by the contraction of two thick fibrous muscles which are fixed internally to each end of the shells; and these shells are lined all around with a membrane or epidermis, which unites them so closely together when they are soaked in water, that not the smallest drop can escape from the muscle. When mussels choose to walk (a), they often contrive to raise themselves on the sharp edge of their shells, and put forth a fleshy substance susceptible of extension, which serves them as a leg to drag themselves along, in a kind of groove or furrow which they form in the sand or mud, and which supports the shell on both sides. In ponds, these furrows are very observable. From the same member or leg hang the threads.

(a) The common sea or edible mussel has, from its being for the most part found fastened to the rocks, been supposed by many wholly incapable of progressive motion; but this M. Reamur has shown to be an erroneous opinion. It is a common practice in France, at such seasons of the year as do not afford sun enough to make salt, to throw the common sea-mussels, which the fishermen catch about the coasts, into the brine-pits. They have an opinion that this renders their flesh the more tender and delicate, as the rain which falls at these seasons makes the water of the pits much less salt than the common sea-water. The mussels are on this occasion thrown carelessly in, in several different parts of the pits; yet, at whatever distances they have been thrown in, the fishermen, when they go to take them out, always find them in a clutter together; and as there is no current of water in these places, nor any other power of motion, which can have brought the mussels together, it seems threads by which the animals fasten (a) themselves to rocks or to one another.

According to the observations of M. Mery of the Paris Academy, and the subsequent experiments of other naturalists, mussels are all androgynous; and, from a peculiar generative organization, each individual is of itself capable of propagating its species, and annually does it without the intercourse of any other. This is altogether singular, and different from what takes place in snails, earthworms, and other hydrogenous or hermaphroditical animals; for though each individual of these contains the parts of both sexes, yet there is always a congress of two animals for the propagation of the species. The parts of generation are

seems very evident that they must voluntarily have marched from the places where they were at first, to have met thus together. This progressive motion is wholly performed by means of what we call the tongue of the mussel, from its shape; but, from its use in this case, appears rather to merit the name of a leg, or an arm, as by laying hold of any distant substance, and then forcibly contracting itself again, it draws along the whole body of the animal. The same part, when it has moved the animal to a proper place, serves also to fix it there, being the organ by which it spins the threads which we call its beard, by which it is held to a rock, or to another mussel. The motion of the mussel, by means of this part, is just the same with that of a man laid flat on his belly, who would draw himself along by laying hold of anything with one hand, and then drawing himself to it.

(a) Mussels are well known to have a power of fastening themselves either to stones, or to one another's shells, in a very strong and firm manner; but the method of doing this was not well understood till the observations of Mr Reaumur explained it. Every one who opens and examines a common mussel, will find, that in the middle of the fish there is placed a little blackish or brownish body resembling a tongue. This in large mussels is near half an inch long, and a little more than a sixth of an inch in breadth, and is narrower at the origin than at the extremity: from the root of this tongue, or that part of it which is fastened to the body of the fish, there are produced a great number of threads, which, when fixed to any solid substance, hold the mussel firmly in its place: these threads are usually from an inch to two inches in length, and in thickness from that of a hair to that of a hog's bristle. They issue out of the shell in that part where it naturally opens, and fix themselves to any thing that lies in their way, to stones, to fragments of shells, or, which is the most common case, to the shells of other mussels; whence it happens that there are usually such large quantities of mussels found together. These threads are expanded on every side, and are usually very numerous, having been found issuing from one shell: they serve the office of so many cables; and, each pulling in its proper direction, they keep the mussel fixed against any force that can be offered from whatever part it come. The filaments are well known to all who eat mussels, who ever carefully separate them under the name of the beard; and Mr Reaumur has found, that while the animal is living in the sea, if they are all torn away by any accident, the creature has a power of substituting others in their room: he found, that if a quantity of mussels were detached from one another and put into a vessel of any kind, and in that plunged into the sea, they in a little time fastened themselves both to the sides of the vessel and to one another's shells; the extremity of each thread seemed in this case to serve in the manner of a hand to seize upon anything that it would fix to, and the other part, which was slenderer and smaller, to do the office of an arm in conducting it.

To know the manner of the mussels performing this operation, this diligent observer put some mussels into a vessel in his chamber, and covered them with sea water; he there saw that they soon began to open their shells, and each put forth that little body before described by its resemblance to a tongue, and at the root of which these threads grow; they extended and shortened this part several times, and thrust it out every way, often giving it not less than two inches in length, and trying before, behind, and on every side with it, what were the proper places to fix their threads at: at the end of these trials they let it remain fixed for some time on the spot which they chose for that purpose, and then drawing it back into the shell with great quickness, it was easy to see that they were then fastened by one of these threads to the spot where it had before touched and remained fixed for a few minutes; and in repeating this workmanship the threads are increased in number one at every time, and being fixed in different places they sustain the fish at rest against any common force.

The several threads were found to be very different from one another; the new formed ones being ever whiter, more glossy, and more transparent than the others; and it appeared on a close examination, that it was not, as might have been most naturally supposed, the office of the tongue to convey the old threads one by one to the new places where they were now to be fixed, but that these in reality were now become useless; and that every thread we see now formed, is a new one made at this time; and in fine, that nature has given to some sea-fishes, as well as to many land-insects, a power of spinning those threads for their necessary uses; and that mussels and the like fish are under water, what caterpillars and spiders are at land.—To be well assured of this, however, Mr Reaumur cut off the beard or old threads of a mussel as close as he could, without injuring the part; and the proof of the opinion of their spinning new ones at pleasure was now brought to this easy trial, whether these mussels, so deprived of their old ones, could fix themselves as soon as others which were possessed of theirs, and could throw out their threads to as considerable distances. two ovaries and two seminal vesicles. Each ovary and vesicle has its proper duct. It is through these four channels that the eggs and the seed of the mussel are conveyed to the anus, where those two principles unite at their issue, which answers the purpose of generation. It is in the spring that mussels lay their eggs; there being none found in them but in winter. M. Lewenhoek, in several mussels which he dissected, discovered numbers of eggs or embryo mussels in the ovarium, appearing as plainly as if he had seen them by the naked eye, and all lying with their sharp ends fastened to the string of vessels by which they receive nourishment. The minute eggs, or embryos, are by the parent placed in due order, and in a very close arrangement on the outside of the shell, where, by means of a gluey matter, they adhere very fast, and continually increase in size and strength, till becoming perfect mussels, they fall off and shift for themselves, leaving the holes where they were placed behind them. This abundance the mussel shells very plainly show, when examined by the microscope, and sometimes the number is 2000 or 3000 in one shell: but it is not certain that these have been all fixed there by the mussel within; for these fish usually lying in great numbers near one another, the embryos of one are often affixed to the shell of another. The fringed edge of the Mytilus mussel, which Lewenhoek calls the beard, has in every minute part of it such variety of motions as is inconceivable; for being composed of longish fibres, each fibre has on both sides a vast many moving particles.

The mussel is infested by several enemies in its own element; according to Reaumur it is in particular the prey of a small shell-fish of the trochus kind. This animal attaches itself to the shell of the mussel, pierces it with a round hole, and introduces a sort of tube five or six lines long, which it turns in a spiral direction, and with which it sucks the substance of the mussel. Mussels are also subject to certain diseases, which have been supposed to be the cause of those bad effects which sometimes happen from the eating of them. These are stated by Dr Moehring, in the 7th vol. of the German Ephemerides, to be the moths and the scab. The roots of the moths being introduced into the shell, the water penetrates through the openings, and gradually dissolves the mussel. The scab is formed by a sort of tubercles which are produced by the dissolution of the shell. Certain small crabs, which are sometimes found in mussels, likewise tend to make them unwholesome.

The experiment proved the truth of the conjecture; for those whose beards or old threads were cut off, fixed themselves as soon as those in which they were left, and spread their threads to as great a distance every way.

When the mechanism of this manufacture was thus far understood, it became a natural desire to inquire into the nature of the part by which it was performed. This has hitherto been mentioned under the name of the tongue, from its shape; but it is truly the arm of the fish; and whenever it happens to be loosened from its company, or fixed in a wrong place, it serves the animal to drag its whole body shell and all along, and to perform its several motions. It fixes itself to some solid body; and then strongly contracting its length, the whole fish must necessarily follow it, and be pulled toward the place where it is fixed. This is an use, however, that this part is so rarely put to, that it is not properly to be esteemed a leg or an arm for this; but, according to its more frequent employment, may much better be denominated the organ by which the threads are spun. Though this body is flat in the manner of a tongue for the greater part of its length, it is however rounded or cylindric about the base or insertion, and it is much smaller there than in any other part: there are several muscular ligaments fastened to it about the root or base, which hold it firmly against the middle of the back of the shell; of these ligaments there are four which are particularly observable, and which serve to move the body in any direction. There runs all along this body a slit or crack, which pierces very deeply into its substance, and divides it as it were into two longitudinal sections; this is properly a canal, and along this is thrown the liquor which serves to form the threads; and it is in this canal or slit that these threads are moulded into their form. Externally, this appears only a small crack or slit, because the two fleshy sections of the parts almost meet and cover it; but it is rounded and deep within, and is surrounded with circular fibres. This canal is carried regularly on from the tip of the tongue, as it is called, to its base, where it becomes cylindric; the cylinder in this part being no other than a close tube or pipe, in which this open canal terminates. The cylindric tube contains a round oblong body, of the nature of the threads, except that it is much larger; and from the extremity of this all the threads are produced, this serving as a great cable to which all the other little cordages dispersed towards different parts are fixed. The tube or pipe in which this large thread is lodged, seems the reservoir of the liquor of which the other threads are formed; all its internal surface being furnished with glands for its secretion.

The mussel, like many other sea-fishes, abounds in this liquor; and if at any time one touch with a finger the base of this spinning organ, one draws away with it a viscid liquor in form of several threads, like those of the caterpillar, spider, and the other spinning land-animals. The threads fix themselves with equal ease to the most smooth and glossy, as to rougher bodies; if the mussels are kept in glass-jars of sea-water, they as firmly fasten themselves to the glass as to any other body. Mussels, be they ever so young, have this property of spinning; and by this means they fasten themselves in vast numbers to anything which they find in the sea. Mr Reaumur has seen them, when as small as millet-seeds, spin plentifully, though their threads, proportioned to their own weight, are much finer and smaller than those of larger mussels. The eating of mussels has sometimes produced erysipelas, inflammations, cutaneous eruptions, inapplicable itching all over the body, great restlessness and agitation; and though these complaints are easily removed by oil, milk, and emetics, and have seldom or never proved mortal, yet they have an alarming aspect, and make the patient suffer grievously. These noxious effects have been supposed to be owing to the mussels or part of them having been diseased. Some authors, however, have pretended that those effects never take place but between the vernal and autumnal equinox; and M. Beunie, physician at Antwerp, in a memoir on this subject, seems inclined to adopt this opinion; for he recommends abstinence from mussels during the months of May, June, July, and August. The cause of these noxious effects in the mussel is, according to this author, altogether accidental. They are occasioned, he says, by a kind of Stella marina, a little sea insect pretty common about the mouth of the Scheldt, which sometimes lodges itself in the mussel in quest of food; and whose spawn is so caustic and inflammatory, that, even when applied outwardly to the skin, it produces itching and swellings that are painful in a high degree. The itching occasioned by touching the spawn of the Stella marina is removed by vinegar; and this known fact induced Dr Beunie to prescribe the internal use of vinegar, after bleeding, evacuations, and emetics. His method consists in recommending a large quantity of refreshing beverage, and, every hour, three ounces of vinegar diluted in water. This remedy, however, seems rather to confirm the opinion of those who impute the disorder in question to an unperceived commencement of putrefaction in the mussel; as vinegar is known to be a powerful antiseptic, and there is no sort of putrefaction more noxious and offensive than that of fish.—Upon the whole, the edulis, or eatable mussel, though a rich food, is difficult of digestion. In its best state it is even noxious to some constitutions; and when affected by disease is in some degree poisonous. Mussels are apt to do most harm when eaten raw. They ought always to be boiled with onions, well washed with vinegar, and seasoned with pepper; and even thus qualified, they should not be eaten to excess or too frequently.

Fresh-water mussels are not so good eating as the sea-mussel. The river mussel, according to M. Poupart, swims in the water, and sometimes appears to flutter on its surface. But we believe it more commonly creeps in the mud, where it remains almost always at rest. The pond mussel is always larger than that which is found in rivers; and it is a more solitary animal. In its motion it makes tracks in the sand and mud, as already observed; and it penetrates into it two or three inches, and sometimes more. Pearls of considerable beauty are found in several river-mussels; of this kind are the Scots mussels, those of Valognes in Lorraine, of St Savinier, of Bavaria, and of the marshes near Augsburg.