M YT1LUS. 
m 
dirty-greenifti-yeHow, lamellate, the plaits curved here 
and there, and befet with hollow grooved nuclei. 
3. Mytilus Irons: Ihell plaited, fmoothifh; one lip 
rough. It inhabits the American Ocean, on coral-beds 5 
the thell is reddilh, bluifli, or brown ; generally oval, 
with the margin plaited on each fide, and denticulate ; 
the lower valve glabrous, and grooved in the middle ; the 
upper valve rough, with raifed dots at the margin, and an 
elevated rib in the middle. 
II. Flat or comprefled into a flattened form, and (lightly 
eared. 
4. Mytilus margaritiferus, the pearl mufcle : fliell flat¬ 
tened, nearly orbicular, with a tranfverfe bale, imbricate, 
with toothed tunics. It is found in the American and 
Indian Seas ; is about eight inches long, and (till broader 
than it is long. The infide is beautifully polithed, pro¬ 
duces the true mother-of-pearl, and frequently the molt 
valuable pearls; the outfide is fometimes fea-green, or 
chefnut, or bloom-colour, with white rays : when the 
outer coat is removed, it has the fame perlaceous luftre 
in the infide: the younger fhells have ears as long as the 
fliell of that divifion of the genus Oftrea called Jcallops. 
The animal is faftened to the upper and lower fhells by 
two white flat pieces of mufcular fubftance, which are 
called by Houttuin ears, and extend about two inches from 
the thick part of the body, growing gradually thinner. 
The extremity of each ear lies loofe, and is lurrounded 
by a double brown fringed line. Thefe lie almolt the 
third of an inch from the outer part of the thell, and are 
continually moved by the animal. Next to thefe, above 
and below, are fituated two other double fringed movable 
fubftances, like the branchiae of a fifh. Thefe ears and 
fringes are joined to a cylindrical piece of flefh of the fize 
of a man’s thumb, which is harder and of a more mufcu¬ 
lar nature than the reft of the body. It lies about the 
centre of the fhells, and is firmly attached to the middle 
of each. This, in faff, is that part of the pearl-fifh which 
ferves to open and fhut the fhells. Where this column is. 
faftened, we find on the flefh deep impreflions; and on 
the fhell various nodes of round or oblong forms, like 
imperfefl pearls. Between this part and tne hinge lies 
the principal body of the animal, feparated from the 
reft, and fhaped like a bag. The mouth is near the hinge 
of the fhell, enveloped in a veil, and has a double flap or 
lip on each fide 5 from thence we obferve the cefophagus 
defcending like a thread to the ftomach. Clofe to the 
mouth there is a curved brownifli tongue, half an inch in 
length, with an obtufe point; on the concave fide of this 
defcends a furrow, which the animal opens and fhuts, and 
probably ufes to convey food to its mouth. Near its mid¬ 
dle are two bluifh fpots, which feem to be the eyes. In 
a pretty deep hole, near the bafe of the tongue, lies the 
beard, byJJ'us, faftened by two flelhy roots, and confifting 
of almolt a hundred fibres, each an inch long, of a dark 
green colour, with a metallic luftre ; they are undivided, 
parallel, and flattened. In general, the beard is more 
than three quarters of an inch without the cleft, o rrima; 
but, if the animal is difturbed, it contracts it conlider- 
ably. The top of each of thefe threads terminates in a 
circular gland, or head, like the ftigrr.a of many plants. 
With this byfl'us they fallen themfelves to rocks, corals, 
and other folid bodies ; by it the young pearl-fifh cling 
to the old ones, and with it the animal procures its food, 
by extending and contracting it at plealure. Small fhell- 
fifli, on which they partly live, are often found clinging 
to the former. The ftomach lies clofe to the root of the 
beard, and has, on its lower fide, a protraCled obtufe 
f ioint. Above the ftomach are two fmall red bodies, like 
un ,s ; and front the ftomach goes a long channel or gut, 
which takes a circuit round the mufcular column above- 
mentioned, and ends in the anus, which lies oppofite to 
the mouth, and is covered with a fmall thin leaf, like a 
fNp. The natives pretend to diltinguifh the fexes by the 
appearance of the fhell j the large flat ones they call males ; 
and thofe that are thick, concave, and vaulted, they call 
females, or pedoo-chippy. 
It is remarkable that fome of thefe animals are as red 
as blood, and that the infide of the fliell is of the fame 
colour, with the ufual pearly luftre; the divers attribute 
this rednefs to the licknefs of the pearl-fifh, though it is 
mod probable that they had it from their firft exiflence. 
In the fliade they will live twenty-four hours after being 
taken out of the water. This animal is eaten by the lower 
clafs of Indians, either frefh in their curries, or cured by 
drying ; in which ftate they are exported to the coaft. 
The above particulars are collected from an “ Account 
of the Pearl-fifliery in the Gulf of Menar, 1797 ; by 
H. Le Beck, Efq.” in the Afiatic Refearches, vol. v. p.. 393, 
For the method of fifhing pearls, and the previous cere¬ 
monies, fee the article Manar, vol. xiv. p. 255. 
The formation of pearls has puzzled both ancient and 
modern naturalifts, and given occafion t»a great number 
of hypothefes, many of them wild and extravagant enough. 
But M. Reaumur, in a very curious piece on the fubject 
of the formation both of the fhells and pearls, (Mem. of 
the French Academy, anno 1717,) obferves, that pearls 
are formed like (tones in animals ; as thofe, e. g. in the 
bladder, kidneys, See. and that they are apparently the 
efteCts of a difeafe of the fifh. In faCt, they are all 
formed of a juice extra vafated out of fome broken velfels, 
and detained and fixed among the membranes. To 
evince the pofllbility of this, he (hows that the fhells of 
fea-fifh, as well as thofe of fnails, &c. are wholly formed, 
of a glutinous ftony matter, oozing out of the body of 
the animal. Now it is no wonder that an animal, which 
has veflels wherein circulates a fuffleient quantity of ftony 
juice to build, thicken, and extend, a fhell, fliould have 
enough to form ftones alfo, in cafe the juice, deftined for 
the growth of the fhell, (hall chance to overflow, and burft 
forth in any cavity of the body, or among the membranes. 
To confirm this fyftem, he obferves, that the inner fur- 
face of the common pearl-mufcle, found on the coafts of 
Provence, is of a pearl or mother-of-pearl colour,, from 
one part of its extent, which he determines, to another; 
after which it becomes reddiih. Now there are pearls of 
two colours found in the fhell; and the colours of the 
pearls are precil'ely the fame with thofe of the fliell ; nay, 
more, each kind of coloured pearl is found in the cor- 
ref’ponding coloured part of the fhell; which {hows, that, 
in the fame place wherein the tranlpiration of a certain 
juice had formed, and would have continued to form, a 
coat or layer of fhell of a cerrain colour, the veflels which 
conveyed that juice being broken, there is formed a little 
mafs or collection of the juice, which, hardening, becomes 
a pearl of the lame colour with the part of the fliell to 
which it correiponds. Add to this, that the filver or 
pearl-coloured part of the fhell is formed of ftrata, or 
layers, over one another, like an onion ; and the reddifti 
part of little cylindrical fhort fibres applied againft one 
another. The pearls of the two colours have alfo this 
difference of texture; not but they are both compofed 
of concentric layers; but thofe of the reddiih pearls are 
much lefs fenfible ; and, befides, they have threads, which, 
like radii, proceed from their centre to theircircumference. 
Thefe circumltances feem effectually to determine the 
formation of pearls, and to ellablifh this'fyftem beyond 
contradiction. 
The extravafations above-mentioned may be caufed by 
heterogeneous bodies, fuch as land, coming in with the 
food, which the animal, to prevent difagreeable friction, 
covers with its glutinous matter, and which, as it is fuc- 
cellively f'ecreted, forms many regular lamellae, in the 
manner of the coats of an onion, or like different ftrata 
of bezoars, only much thinner; this is probable; for, if 
we cut through the centre of a pearl, we often find a fo¬ 
reign particle, which ought to be confidered as the nu¬ 
cleus, or primary caul'e of its formation. Tne loofe 
pearls may originally have been produced within the 
body, and on their increale may have feparated and fallen 
to 
