M Y T 
Tie under fhells, fand, or mud, without being perceived, 
and yet mufcles may be produced from them. 
“ Having taken l'ome of the unformed mufcles out of 
the eggs, I caufed a drawing to be made of their figure, 
as near as the engraver was able to imitate it: this is 
fhown at fig. 4, F G, which reprefents fuch an unformed 
mufcle, incloied in its membrane or covering, in which 
the ftreaks before-mentioned did not appear until the 
greateft part of the moifture thereof was evaporated. 
Fig. 5, H I K, (hows another of them, the ftreaks or 
veflels in which, between I and K, appear feparated, or 
fundered from each other; and this w-as done in the tak¬ 
ing it out of the egg, being in that operation deprived of 
the furrounding membrane or fkin. At the latter end 
ef April, when I had finifhed the preceding obfervations, 
I received a large jar full of mufcles out of Zealand ; upon 
examination of which, I was much furprifed to fee that 
molt of the fhells were quite frnooth and polifhed, being 
not only deftitute of eggs, but, for the mod part, bare of 
the membrane which gives them a blackifh colour, fo that 
they now appeared of a lively blue; however, I found 
four or five with perfect eggs on them, and in them were 
young mufcles : fome of thel’e I took out of the eggs, and 
now plainly faw, that what 1 had at firft taken for the un¬ 
formed mufcle, was, in fadt, only the ligament, or firing, 
whereby the young mufcle was nourilhed. A drawing of 
the real lhape, as it now appeared to me, is given at fig. 6, 
where G H I reprefents the ligaments of the unformed 
young mufcles, and I K the mufcle itfelf: another of 
them is reprefented at fig. 7, where L M (hows the firings 
or ligaments, and M N the mufcle; and this laft figure, 
I think, exhibits the true form of the young mufcle, as 
it lies in the egg; and, from thefe laft obfervations, it 
appears that the parts reprefented in fig. 4, at G, and in 
fig. 5> at H, were only the fubftance, or matter, from 
whence the mufcle would be formed, and which, at the 
time when that drawing was made, had not come to 
fufficient perfection to render the parts diftinguifhable. 
“ In the courfe of the laft obfervations, I examined 
that hard and variegated, or marbly-coloured, part, lying 
in the middle of the mufcle, which fome cail the heart, 
and others take to be the tongue, of this fifh; and when, 
upon opening the mufcle, I cut out this part, and placed 
it before the microfcope, I obferved fo tremulous or qui¬ 
vering a motion in the furface, as if millions of little 
living creatures were running about upon it; befides an¬ 
other motion, which the part had to and fro. This part 
the mufcle can extend fo far, that I think it will almoft 
reach all over the (hell, which made me think that, per¬ 
haps, by this organ, the eggs are placed on the fhell in the 
regular order I have before def'cribed.” 
12. Mytilus incurvatus; (hell very crooked on one fide 
near the beaks, then greatly dilated ; within it is marked 
with a violet tinge. Found on the Anglefea coaft: the 
ftlell is covered with a thick rough, fkin. 
13. Mytilus pellucidus: fhell oval, tranfparent, and 
very elegantly radiate lengthways with purple and blue. 
This, like the laft, is found at Anglefea, in oyfter-beds; 
and is about two inches long. 
14. Mytilus umbilicatus: fhell contracted into a deep 
rugged cavity oppofite the hinge, forming a deep hollow 
when the valves are clofed. It is found at Anglefea, 
and is nearly five inches long; the fhell is oval, refembling 
the M. modiolus, defcribed farther on; but it is diftin- 
guifhed by the remarkable indentation near the beaks. 
15. Mytilus curtus: fhell fhort, ventricofe, obtufe at 
the beaks, and of a dirty yellow. It is found at Wey¬ 
mouth. 
16. Mytilus ungulatus: fhell frnooth and (lightly curved; 
hind margin inflected;.-hinge terminal and two-toothed. 
Inhabits the Mediterranean and Cape of Good Hope. 
( 3 . There is a variety of this fpecies found at New 
Zealand, that refembles the. M. edulis, but is full five 
inches long, and two inches and a half broad : the valves 
are very convex, refembling the hoof of an ox* 
I L U S. 493 
17. Mytilus bidens: fhell ftriate, (lightly curved, the 
hind margin inflected ; the hinge terminal and two-tooth¬ 
ed. Inhabits the Mediterranean, Ethiopic, Atlantic, and 
Magellanic, feas. 
t8 . Mytilus modiolus : fhell frnooth and blackifh, ob¬ 
tufe at the fmaller end, and rounded at the other, one 
fide near the beaks is angular. Two varieties are noticed 
by Lifter. It inhabits the European, American, and 
Indian, feas, adhering to fuci and zoophytes; is fix or 
feven inches long, and about half as broad ; the fifh is red 
or orange, and eatable. The lower fhell, open, with the 
contained animal, of the natural fize, is fhown at fig. 8. 
19 Mytilus cygneus : fhell ovate, very brittle, and 
tranfverfely wrinkled ; the anterior end compreffed ; the 
other rounded ; the hinge lateral. Two varieties of this 
fpecies are noticed by Lifter. It is frequently found in 
rivers and ponds ; is about two or three inches broad, and 
three inches long; the fhell is deep, and within it is white, 
opaque, and often rough, with finall pearls. 
20. Mytilus anatinus, the duck-mufcle, orpeat-mufcle: 
fhell ovate, a little compreffed, very brittle and ferni- 
tranfparent, with a membranaceous margin; the beaks 
are decuticated. It inhabits the frefh waters of Great 
Britain, and of other parts of Europe; it is about five 
inches long, and half as broad. Ducks and crows are 
extremely fond of this fpecies, and of the M. cygneus; 
and the crows, when the fhell is too hard for their bills, 
fly up with it to a great height, drop the fhell on a rock, 
and pick out the meat after the fhell is thus broken. The 
following remarks of M. Leeuwenhoek feem to apply to 
this fpecies, as to its power of loco-motion, which we 
have before noticed in the M. margaritifera. 
“ I have obferved, that, when ou-r navigable canals here 
in Holland, or our ditches, are cleaned, a kind of large 
fifh are taken from the bottom, named by us, veen mojjelen, 
or peat-muf’cles. Of thefe I procured fome, which were 
about three or four inches long, with very thin fhells. A. 
countryman, whom I faw collecting thefe lhell-fifh, told 
me they were to be found under the banks, and in the 
(hallow parts of the ditches, or canals, among the leaves 
>and twigs, or other litter 5 and, indeed, I have feen them 
taken in thofe places; but, as I was certain that thefe 
(hallow places were frozen to the bottom in the winter, 
which the fhell-fifh could not furvive, I was told that 
they had a power of moving from place to place. To fa- 
tisfy myfelf in this refpedi, I made two experiments on 
thefe mufcles, of which I put fix or eight into an earthen 
veflel, with a flat bottom, and poured on them fome of 
the fame water in which they were taken : this veflel I 
placed in my ftudy, and I found that in a few hours time 
they had all changed their pofitions, and had approached 
nearer together than they were when firft placed in the 
veflel. And I obferved that thefe mufcles, about the 
middle of their fhells, thruft out, through the opening, 
a flefhy fubftance, or organ, about two-third parts the 
length of the fhell : this part was about half an inch 
broad, and fharp at the end ; and, in order to move them- 
felves from place to place, they thruft this organ under 
their fhell, and, applying it with a quick motion to the 
bottom of the place where they lay, could by this means 
not only change their pofture, but turn themfelves upfide 
down. 
“ At the end of the month of Auguft, upon opening 
fix of thefe mufcles, I found many eggs within them, 
which, were fo perfedf, that I could diftinguifh the newly- 
formed fhells, fo that they were not fo properly to be 
named eggs as unborn peat-mufcles. Two of the parent 
mufcles were fo fmall, that I judged they were not above 
a year old, whereas the others were, in my opinion, fix,. 
eight, or nine, years old; but the.young mufcles were of 
the fame fize in all of them. In the beginning of Septem¬ 
ber, I procured about fifty more of thefe mufcles, and, 
upon opening twelve of them, I found two, wherein the 
oung ones leemed to be fo perfect, that they would pro— 
ably foon be excluded from, the parent. I always found 
that* 
