The servant, who put the Marquis upon this stratagem, had previously assured his master that these pearls withstood heat and moisture; that they were not easily scratched, and that their weight was the same with that of real pearls. This anecdote, which is detailed by Professor Beckman, proves that artificial pearls did not become common, even in France, till many years after their first invention. The trade of artificial pearl-making is still carried on at Paris by the descendants of Jacquin, the original inventor; but they are also made in many other parts of Europe, and with several variations as to the colour and kind of the glass, and other minute particulars. The mytilus margaritiferus of Linnæus, or great pearl muscle, is not the only shell which produces pearls. A species of the genus called mya, and which is the mya margaritifera of Linuæus, also produces pearls, though, in general, of a far smaller size, and of inferior quality. This shell is commonly called the European pearl muscle, and much resembles the common river muscle, though of a different genus. It is found in rivers in the north of England, in Scotland, Ireland, and many other parts of Europe. In the seventeenth century several rich pearls of large size are said to have been obtained from this shell, in some of the rivers of Ireland, One was valued at upwards of 4., another at 10., and a third at no less than 40%. As a species, the European pearl-muscle, or more properly, mya, is distinguished by having a thick, coarse, blackish shell, generally barked or decorticated towards the hinge *. I have before mentioned, when speaking of the real or Indian pearl-shell, the French art of making artificial pearls. There exists also an art, said to be often practised by the Chinese, and which Linnæus attempted to put in practice in Europe, of forcing, as it were, the production of pearls, in the mya margaritifera, or European pearl muscle, by piercing the outside of the shell in several places, so as barely not to make complete perforations. In this case, the animal, conscious of the weakness or deficiency of the shell in those spots, soon begins to secure the weakened parts by depo. * Pearly concretions are also occasionally formed in all shells, and are of different colours, according to that of the shell in which they are formed. Thus, the animal of the large univalve shell, called the strombus gigas, or great rose-mouthed strombus, sometimes produces pearly concretions of a fine rosecolour. siting over them a great quantity of its pearly calcareous matter, and thus forms so many pearly tubercles over them. The practice how. ever is, I believe, considered as not of importance sufficient to make it an object of gain, but rather of mere curiosity; the pearly tubercles thus obtained being of inferior beauty to those more naturally produced. [Shaw. 2. Great Clamp Shell. Chama Gigas.-LINN. This is by far the largest and heaviest of the testaceous tribes. The animal, and even the shell itself, has a considerable resemblance to an immense oyster. The shell is plated, however, with arched scales; the posterior slope gaping with a crenulate margin. It is an inhabitant of the Indian Seas, and has sometimes been found of more than three feet long, and five hundred pounds in weight; the fleshy part, or inhabitant, large enough to furnish a hundred and twenty-seven men with a good meal; and strong enough to cut asunder a cable, and lop off men's hands. Specimens of this shell in its full growth are not very common, from its being unwieldy ; but they may be seen in the British Museum. [Lister. Klein. Editor. 3. Sea-Pinna. Pinna rudis.-LINN. The animal in this genus of shell-worms, is considered by Linnæus as allied to a Limax or slug, and consequently to the snail tribe also. Some of the species and varieties of pinna are very large shells, of a thin structure in proportion to their size and they are generally affixed to rocks or other objects, by a large tuft of very fine but strong silken fibres or threads, which the animal has the power of forming, by thrusting out a kind of pointed trunk, with which it touches the object it wishes to adhere to, and by retracting it, forms a glutinous thread; and, by the repetition of this motion, forms the whole tuft by which it is fastened. The large sea-pinna, or pinna rudis, is a curious instance of this. This shell is brown externally, with a slightly iridescent silvery cast within; of a lengthened shape, with a very narrow base, and dilated and rounded towards the extremity. It is a frequent inhabitant of the European coasts; and in some places, as about the coasts of Sicily and Italy, the silken tufts are often collected, and spun into various articles of dress, as gloves in particular; the silk requiring no dye, but retaining its native colour, which is an elegant, glossy, yellowish brown. Specimens of this kind of silk are generally to be seen in most of our museums. Neither is this faculty of fastening, or anchoring by means of silken fibres, confined to the genus pinna, but takes place, as we have already seen, in the genus my tilus, and probably in some of the rest. [Shaw. The MULTIVALVES, or shell-worms, whose shell consists of three or more than three parts. And of these there are but three described kinds; the chiton, lepas, and phloas; the last of which is worthy of notice on various accounts; the shell is bivalve, with several shallow differently shaped accessory shells at the hinge; hiuges recurved, united by a cartilage; in the inside beneath the hinge is an incurved tooth. The inhabitants of this genus perforate clay, spongy stones, and wood, while in their younger state : and as they increase in size, enlarge their habitation within, and thus become imprisoned: they contain a phosphorous liquor of great brilliancy in the dark, and which illuminates whatever it touches or happens to fall upon. It is equally extraordinary by what means this curious worm is able to burrow and work its way in the midst of massy stones, as the nature of the phosphorous light which it so copiously secretes. The organ by which it appears to work is a fleshy substance, placed near the lower extremity of the shell, of the shape of a lozenge, and con siderably large in proportion to the size of the animal; it is by perseverance alone, therefore, and by great length of time, that it is able to scoop out an augmentation to the cavity it inhabits. The minute opening by which the worm, when very small, insinuated itself into the interior of the substance it inhabits, is generally to be traced; and at once subverts the absurd opinion of those who have asserted that the phloas is at first hatched in these holes. The light emitted is of a very peculiar kind. Its existence has been long known, for it is noticed by Pliny, who observes that it shines in the mouth of the person who eats it, and makes him lumi nous if it touch but his hand or clothes. Putrescency, though not putrefaction, is necessary for the discharge of the light possessed by phosphorescent fishes; in the philoas, on the contrary, the light is rendered brighter in proportion to the freshness of the animal. The moisture of salt or fresh water revives it; brandy suddenly extinguishes it; vinegar not quite so soon. It is probable that this worm often contributes to the luminous appearance of the sea. Various experiments have been made to render the light or luminous matter secreted by the phloas permanent, but none have altogether succeeded. Reaumur kneaded the juice into paste with flour, and found that the paste would give light when immersed in warm water. But the best way to preserve the light, is to preserve the worm, or fish, as it is usually called, in honey; in which state, whenever taken out, and plunged in warm water, it will give a very brilliant light for a twelvemonth afterwards. Milk, however, appears to be rendered more luminous by this phosphorous matter than any other liquid; a single phloas made seven ounces of milk so luminous, that the faces of persons in the dark could be seen and distinguished by it. There are twelve species of this curious animal; three of which are common to the seas of our own coast. [Pantologia. SECTION VI. Intestinal Worms. : THESE are more properly called worms than any of the preceding. They are ordinally characterised as simple, naked animals, without limbs of any kind and derive their ordinal name from inhabiting the bowels of the earth, water, or animals of various kinds. Among the more common tribes we may mention the lumbricus or earth-worm, including the dew and the lug; the hirudo or leech; the limax or slug; the ascaris, comprehending both the thread and the long mud intestinal worm; and the tænia or tapeworm. Among the more curious are the furia, the gordius or hairworm, and the filaria, or Guinea.worm. 1. Hair-worm. Gordius aquaticus.-LINN. This resembles a horse-hair in its shape, and is hence often de nominated horse-hair worm, or seta equina. It inhabits soft stagnant waters, is from four to six inches long; and twists itself into various knots and contortions. Linnæus asserts, that in Sweden its bite or sting is supposed to produce the complaint called a whitlow, and that he once knew this rumour verified and Dr. Shaw declares that he also once beheld the complaint follow upon the sting of a gordius, though he leaves it doubtful whether the complaint might not have occurred, if the sting had not been inflicted. [Nat. Miscel. Turton. Linn. 2. Guinea Worm. Filaria medinensis. In this genus of worms the body is round, filiform, equal and quite smooth; mouth dilated, with a roundish lip. There are eigh teen species: The division A. is found in different varieties in man, the cel lular membrane of the horse, in the lion, the martin, and bare. B. In hawks, owls, crows, storks, and poultry. C. In the scarabæns fimetarius; silpha obscura, carabas, and gryllus. D. In the papilio articæ; p. betulæ ; p. quercus; sphinx Euphorbiæ; phalana caja; ph. quercus; ph. pellionella; found under the skin of the larves, and very destructive to them; sometimes solitary, and from four to seven inches long. The species chiefly worthy of notice is, F. medinensis, of the division A, is the dracunculus, or Guinea-worm. The body is entirely pale yellowish. It inhabits both the Indies, and is frequently in the morning dew, whence it enters the naked feet of the slaves, and creates the most troublesome itchings, generally accompanied with inflammation and fever. It must be cau |