The Common Mussel.
'Travelling is not good for us; we travel so seldom. How much more
dignified leisure _hath a Mussel glued to his impassable rocky limit
two inches square_! He hears the tide roll over him, backwards and
forwards, twice a day (as the Salisbury coach goes and returns in eight
and forty hours), but knows better than to take an outside place on
the top on't. _He is the owl of the sea, Minerva's fish_, the _fish of
wisdom_.'
C. LAMB to B. BARTON.
[Illustration:
1 COMMON MUSSEL (_Mytilus edulis_)
a The foot
b The byssus
c c Muscles which regulate the action of the foot
2 THE MUSSEL CLOSED
3 THE BERÖE (_Cydippe pileus_)
4 THE FAN AMPHITRITE (_A. ventilabrum_)]
XI.
In his celebrated journey to the western islands of Scotland, Dr.
Johnson tells us that when at Ulinish, hearing of a cavern by the
sea-side remarkable for powerful reverberations of sound, he determined
to pay a visit to the spot. After dinner, having procured the services
of some boatmen, the doctor, in company with Bozzy, started off on
his trip, which, on the whole, appears to have been a pleasant one.
There was, however, no _echo_ to be heard; but to make up for this
disappointment, Mr. Boswell went angling, and caught a wee 'cuddy,'
(a fish about the size of a gudgeon), while the doctor was gratified
by the sight of some sea-weed growing upon stones, and above all, at
witnessing for the first time _Mussels in their natural state_.
The impression made by this candid acknowledgment upon our minds
is one of wonder, that a man like Johnson could have reached his
advanced years without having seen so common a sight. But it is
possible that even in our day, with its unprecedented facilities
for cheap travelling for the most inland inhabitants, there may be
many persons to whom the sight of a Mussel fixed to a boulder by its
self-constructed cable, would be as great a novelty as it was to the
eloquent author of Rasselas.
It is, however, one of the commonest appearances which meet the eye of
those in the habit of visiting the sea-shore. At certain localities
myriads of Mussels may be noticed attached to the surface of the rocks.
So thickly are these sometimes covered over, that the blade of a knife
cannot be inserted at any part without touching one or more of the
esculent bivalves that are to form the subject of this chapter.
The Mussel anchors itself by means of the Byssus; or, as it is commonly
termed, the 'beard.' This appendage is composed of various slender
threads which are attached to any object within reach, whether such be
the shell of a neighbouring Mussel, a small stone, or huge boulder.
The members of each colony are thereby bound together, it may be
figuratively said, by the silken cords of friendship, and mayhap of
love. The _Mytili_ evidently believe that 'there's no place like home.'
Although gifted with a power of moving about at will, they never
attempt to exercise this when living together in a family circle,
but pass through life's stages upon the spot where they were born.
Certainly, if there be such a sight as a truly happy and contented
family in the marine animal kingdom, it is to be found exemplified in
these bearded molluscs.
As hinted, they live shoulder to shoulder, back to back, and otherwise
mutually support each other. They need not look about for a single
meal, but have merely to allow themselves to be fed by the waves, which
yield them a constant supply of fresh and wholesome food. Their sole
duty in this respect is limited to the selection of objects suitable
to their palate. Their 'at homes' being so frequent, the _Mytili_ can
boast of a large circle of acquaintances. The Periwinkle, and his
friend Silver Willie, often make a morning call, take pot luck, as it
is termed, and then politely retire. _Mr. Carcinus Mænas_ and his poor
and dirty relation, _Maia Squinado_, perchance look in of an evening.
_Solaster Papposa_, or occasionally the lanky-legged _Uraster Rubens_,
and other 'stars' of the marine world, crawl in at unseasonable hours
in their usual lazy style, and are generally rewarded by finding the
doors (valves) shut against them. This 'cut direct' does not appear to
be at all annoying; or if so, the Star-fishes are too cunning to show
it, for they quietly saunter away as if they never had the slightest
wish to put their feet within their neighbour's dwelling.
There is a 'black sheep,' as Sir Pertinax Mac Sycophant would say, who
intrudes himself into Mussel society, and plays sad havoc among its
members. This crawling rascal is the wolf of all Musseldom flocks.
Young and old alike experience the blighting effects of his villanous
propensities. The name of this obnoxious personage is _Purpura
Lapillus_ (Common Whelk). What, the reader will ask in surprise, a
univalve prey upon a bivalve? Is that possible? It is, unfortunately,
too true.
If we take a Mussel in our hand we shall find it perfectly impossible
to force its valves asunder, without the aid of a strong knife or other
instrument; yet the Common Whelk, fleshy and insignificant creature
though it be, will consume the animal within, and make the valves
fly open in a brief space of time, by means of its soft tongue. But
leaving such general remarks, let us suppose we are standing before a
boulder covered with these mussels. Numbers of gaping shells may be at
intervals perceived still attached to the rock, but with the interior
of each valve so empty and smooth, that we could scarce believe they
had ever embraced a living occupant. On taking up one of the valves and
closely examining it, do you observe nothing peculiar about it now?
'No.' Take up the other then, and submit it to a similar inspection.
Well, what do you see now? 'Nothing,' you still reply, 'unless it be a
peculiar little hole about the size of a pin's head, which surely is
of no importance.' That little hole was of _vital_ importance to the
poor mollusc, for through that aperture the life and substance of the
Mytilus was drawn by the voracious Purpura.
But the poor Mussel is exposed to the attacks of other enemies--aquatic
birds, as sea-gulls and ducks, eagles, vultures. Even water-rats and
monkeys may also be included in the list.
It is amusing to see a gull, by no means a foolish bird, standing
patiently before a Limpet, for example. The animal, unsuspicious of the
presence of an enemy, raises his canopy with the view of relaxing his
overstrained muscles, and is instantly toppled over by the intruding
beak of the bird. If unsuccessful in his first attempt, the gull is
well aware it would be useless to try a second time at that tide.
But if a Mussel be the object of attack, it is wrenched from its seat,
raised to a certain height, and then allowed to drop upon a stone with
the view of breaking the shell. In one locality called Mussel Bay, Mr.
Barrow says he disturbed some thousands of birds, and found so many
thousands of shell-fish scattered over the surface of a heap of shells,
that, for aught he knew, would have filled as many thousand waggons.
This habit of the feathered tribe was, by the way, well known to the
ancients, and I may be pardoned relieving my pages by a quotation on
the subject from the 'Shepherd's Calender' of Spenser, whose exquisite
descriptions of natural history are as marvellous as his allegorical
poem. The author of the 'Fairy Queen' thus humorously reads a lesson
to an ambitious man,--
"He is a shepherd in gree,
But hath been long ypent,
One day he sat upon a hill,
As now thou wouldst mee;
But I am taught by Algrinds ill,
To love the lowe degree.
For sitting so, with barred scalpe,
An eagle soared hye,
_That weening his white head was chalke,
A shell-fish down let flye!
She weened the shell-fish to have broke,
But therewith bruised his brayne_,
So now astoined with the stroke,
Hee lyes in lingering payne!"
It seems remarkable that the 'illustrious French naturalist,' Reaumur,
should have been the first, if not to discover, at least to publish,
any description of the manner in which the Mussel spins its silken
cable. Yet one hour's experience in a tea-cup or tumbler will exhibit
most of the features in this interesting process.
That Reaumur's narrative, although usually copied by most writers of
the present day, is not strictly correct, and, moreover, that the foot
of the mussel is _not_ 'useless as an instrument of progression' (as
generally asserted), may be easily proved to the satisfaction of the
student by adopting some such simple experiment as that which I am now
about to describe:--
Being at the sea-side on a fine summer afternoon, I procured three
specimens (I might have had as many hundreds if disposed) of the
Mytilus. On my return home I placed them in a common tumbler, and
waited patiently to see the result. My object was, if possible, to
witness the manner in which this animal grows its beard.
In less than five minutes an industrious little fellow, whom we will
call No. 1, gently opened his shell, and immediately protruded his
fleshy foot until it reached a length of nearly two inches. So far as I
could determine, the design of the Mussel was to discover, in the first
place, what kind of a lodging he occupied; whether or not he had any
companions; and also, to know if these or any other objects could be
found worthy of his _attachment_.
Sometimes the foot would be protruded under the shell, then in a
contrary direction. Or by an exertion of the strong muscular power
which that organ possesses, the entire shell would be lifted off the
ground and urged forward to a considerable distance. Of course he soon
come in contact with a neighbour Mussel, whom we may term No. 2, but as
the latter was not anchored by any byssus, he was speedily pushed on,
and on, until No. 3 was met, and the latter, in his turn, made to take
up a new position.
Being tired of wandering about, No. 1 then extended his foot along the
base of the vase to a certain point, and there let it rest for a few
seconds. When again withdrawn, to my great delight, I saw the first
thread of a new byssus had been constructed.
As my principal object was to become acquainted with the mode of
formation of the beard, I did not feel satisfied with merely watching
the movements of the animal from above. After a brief interval another
thread was spun. I bore in mind the words of Reaumur, who says, 'The
Mussel never spins more than four or five threads in the twenty-four
hours.' Aware that no time must be lost, though still afraid to disturb
the mollusc lest it might suspend its labours, I instantly detached
my specimen, and again turned its shell round so as to bring the
opening of the valves against the face of the glass. The creature did
not seem at all offended at his handiwork having been destroyed, but
still obstinately refused to let me see the working of its foot. Again
was the shell rolled over, and again did I replace it in its former
position. This time, in order to keep it from being shifted, a stone
was deposited upon the valve. Nothing daunted, the animal gradually
separated the valves of its shell, and at the same time advanced and
elevated its foot to the exact position that I had so long desired.
The spinner, when at its full length, was pressed firmly upon the
flat surface of the glass, and there allowed to remain for a while.
Suddenly, at nearly _half an inch distance from its extreme end_ (or
point), a little mouth was seen to form, about the size of a large
pin's head, from which there issued a milk-white fluid, that gradually
hardened and became fixed to the glass. This object being light in
colour, had a pretty effect when contrasted with the rich brown tint
of the spinner. Shortly afterwards the foot rolled over and withdrew
into the shell, leaving behind it the silken thread which had just been
spun. The 'little mouth,' above described, was, if I may so term it,
the mould in which the end of the thread was cast.
In the course of two hours a bundle of byssus threads, sixteen in
number, were produced by this industrious little labourer.
Having thus seen that the foot is useful to the Mussel as an instrument
of progression _before_ the beard is formed, let me now endeavour
to show that it is, at times, of equal service for the same object,
_after_, and when the mollusc is anchored thereby to any particular
spot.
When we remember that this anchorage is formed of a harp-like set of
strings, amounting to ten or even _a hundred_ in number, it does seem
an almost incredible fact that the Mytilus is enabled to change its
station, even when living in single blessedness.
To see a Mussel 'flit,' is a sight one may often watch and wait
for without success. On the other hand, when least expected, the
self-willed mollusc may commence operations. When about to take up
a new home, the animal shaves off its beard entirely, or in more
scientific language, 'rejects its byssus' altogether. In order to
excite the locomotive instincts of my specimens, I used to cut all
the threads of their cable except one. The animal being suspended, of
course its whole weight was then thrown upon a single fibre. Such a
state of insecurity was by no means agreeable, and I generally found in
the course of a few hours that fresh threads were rapidly thrown out,
and an entirely new byssus formed; the old one, which was broken off at
the root, being left behind as useless.
Another singular peculiarity of the Mussel which came under my
observation has not been, so far as I am aware, noticed by previous
naturalists. I allude to the power which the animal possesses of
lengthening out the root or stem of the beard, apparently to an
unlimited extent. This power appears to be seldom exercised, for
although I have had hundreds of specimens of the Mytili, in only one
instance have I witnessed the phenomenon in question.
A large specimen of this bivalve, procured accidentally from a fishwife
in the street, was dropped into the aquarium, and placed close against
the surface of the glass. The animal seemed highly delighted with its
change of situation, for in a few moments the valves were opened, and
a long draught of water taken in to bathe its branchiæ, and furnish
a hearty meal. Having satisfied its appetite, the next process, of
course, was to find out what kind of a home he had been introduced
into. The foot, a noble specimen, was soon protruded, and one after
the other, in rapid succession, various threads were formed. By next
morning the animal, advancing by a series of easy stages, had reached
the surface of the water, which was exactly five inches deep. I knew
it would not remain long in this position, and was anxious to discover
what plan would next be adopted. Several courses were open to him.
For instance, like a marine Captain Cook, he might circumnavigate his
little _Globe_,--or he might let go his cable and drop plump to the
bottom,--or he could follow the route I had often seen taken by his
relations, viz., to journey back to the place from whence he started.
It pleased him, however, to strike out into a new path,--to devise a
method of his own. While located near the top of the tank, he threw out
exactly ninety-eight threads, not certainly for security, but merely,
it would appear, for pleasure.
Then slowly but surely, day by day, he lengthened out the stem of his
byssus tree, until it reached the extreme length of nearly five inches.
To what further degree it would have been extended, had the mollusc not
reached the base of the tank, it is impossible to conjecture.
No sooner did the shell touch terra firma, than the cable which had
taken so long to spin was immediately broken off. I have succeeded in
keeping the same animal by me for the last twelve months, but have seen
no attempt at a renewal of the operation, in the progress of which I
had taken so lively an interest. I may add that this Mussel taught me
another lesson; it was this: in my early studies regarding the habits
of the Mytilus, I had adopted a certain theory of the manner in which
the beard was formed; and having watched so long, and witnessed the
process so repeatedly, I thought myself justified in forming certain
conclusions. My belief was that the creature could not form more than
one thread at a time, _without withdrawing its foot into the shell_, as
I believed, in order to procure a fresh supply of material. That this
notion was erroneous, this animal proved to my entire satisfaction. Not
only may one, but two, three, four, and even six threads be attached
to any selected object, the point of the foot being passed from one
position to another, without the organ being withdrawn into the valves
until the whole of the threads are formed. How many more the Mussel is
capable of producing at one 'stretch,' I have no means of knowing, but
six is the largest number that any of my specimens in such case have
ever fabricated.
The general idea seems to be that the Mussel works in the same manner
as the spider, who emits a drop of liquid against some foreign
substance, which, being allowed to harden somewhat, is then drawn out
as the spider recedes. This notion, I may state, is quite erroneous.
When the sucker of which we have spoken is formed, _the thread is
completed_. It is true that the foot as it retires into the shell
generally glides down the newly-constructed filament, but this is not
of necessity, nor does such circumstance invariably occur. Indeed,
while busily engaged in attaching a disc to the glass, the muscles of
the foot will contract, and thus throw open the folds of the groove,
situated in the middle of that organ; when thus exposed, the byssus
thread may be seen in the furrow, stretched like the string of a harp
or dulcimer.
While the end of the thread is being attached to a certain spot, a
conspicuous muscular action is perceived going on in the foot, which
alternately swells and contracts, as if something were being pumped
up through the byssal channel, until it reached a certain point.
There being dilated and spread out in successive layers, it assumes a
trumpet-like disc, which is firmly fixed to the foreign object. Indeed,
I am by no means certain that the thread is not, when first produced,
exactly like a trumpet in shape. It also conveys the idea of being
blown out in a similar manner to a piece of bottle glass. After being
exposed to the air for some little time, the hollowness of the thread
is not so apparent as when it is newly fabricated.
The mucous fluid, from which the fibres are formed, is secreted in
a gland situated at the base of the foot, whence it is apparently
expelled at the will of the animal into the furrow already referred
to, and is there spun into threads. The toughness of these filaments,
considering that each is finer than the thinnest strand of silk, is
remarkable. Their strength, however, may be easily accounted for,
when we know that each is composed in reality of innumerable delicate
threads, bound together by a subtle gelatinous fluid. This phenomenon
may be made out quite distinctly with a common hand lens, if the
following simple experiment be adopted: Make a Mussel construct its
thread in such a way that the disc of each is planted on the face of
the glass. Then place the fine point of a common needle upon the outer
edge of a chosen disc or sucker, and gently draw the former away to
a little distance, and you will find that by so doing the stretched
string becomes _peeled_. Continue this process carefully, and before
the thread gives way you will have divided it into a dozen parts at
least, all of which are visible to the naked eye, but clearer when the
hand lens is used, and still more distinctly and beautifully defined,
of course, if the microscope be brought into play.
The foot of the Mussel appears to be firmly strapped on, as it were,
to certain transverse muscles, by a contraction of which the animal
closes its shell with surprising force. This strap, composed of a
powerful tendon which passes under the adductor muscles, is attached at
either end to the base of the foot. Thus we account for the remarkable
strength which is evidently seated in the foot, and makes it of so much
importance to the animal. At first sight nothing appears more easy
than to pluck out this organ by the roots, but an attempt will prove
the experiment to be more difficult than many persons suppose.
The colour of the foot varies considerably in different specimens,
even of the same species. Some, for instance, are of a chestnut brown;
others of a kind of mauve or purple, covered with a peach-like bloom
during life; others, again, are of a deep-toned umber, while not a few
are pearly white, and streaked sometimes with pink like a tulip.
The peculiarity of the Mussel to attach itself to foreign substances
has been taken advantage of for the benefit of man, and a curious
instance is exhibited at Bideford in Devonshire, at which town there is
a bridge of twenty-four arches, stretching across the Torridge river
near its junction with the Taw. 'At this bridge the tide flows so
rapidly that it cannot be kept in repair by mortar. The corporation,
therefore, keep boats in employ to bring mussels to it, and the
interstices of the bridge are filled by hand with these mussels. It is
supported from being driven away entirely by the strong threads these
mussels fix to the stonework.'
Like most other writers who quote this strange account, I have not
had ocular proof of its accuracy.[9] That it is quite probable I can
readily believe, as a pretty experiment will partly prove it to any
spirited aquarian. Following out the above idea of the bridge at
Bideford, I managed to build an exceedingly pretty centre piece for my
tank.
[9] Since writing the above, I have received the following interesting
epistle from Mr. Edward Capern, the celebrated 'poet and rural postman'
of Bideford, who kindly sought out the information I desired, relative
to the present state of the bridge above alluded to:--
Bideford, January 27, 1859.
DEAR SIR,--I have inquired of the bridge warder, and he informs me that
the feoffees of the bridge command mussels to be brought up by the
cart-load, to protect the foundation, which is laid on _rubble_.
I am pleased that it has been in my power to procure this information
for you--I am, dear sir, faithfully yours,
EDWARD CAPERN.
Having no ready means of making a rock arch, I collected such pieces
of rock, stones, &c., with weeds attached, as I thought would answer
my purpose, and then proceeded to fabricate the object of my wishes in
the following simple way: First were laid two stones parallel to each
other at three or four inches apart. Upon these I placed a large piece
of rock in a transverse direction. Between the interstices a number
of small mussels were then inserted. When fully satisfied that the
bivalves had moored themselves, I gradually piled one piece of rock
upon another until the structure reached the desired height, each piece
being bound to its neighbour by means of the byssus threads of the
Mytili.
Before each block of stone that formed the foundations of the arch
was placed a splendid frond of Lettuce Ulva, tied by a strand of
silk to a white pebble. These verdant fronds, so smooth in texture
and so gracefully convoluted, rising up from the base of the tank
and reaching to its brim,--mingling, too, with the various tufts of
corallines and other sea-weeds that jutted from each crevice, were
very pretty to look at. When disturbed by the movements of the fishes
passing in and out, the gracefulness and beauty of the sea-weed was
doubly increased.
In making observations upon any bivalve, such as the Mussel, it is
extremely puzzling to know what is going on _inside_ the shell.
Yet it is almost necessary to acquire this knowledge by means not
always apparent, in order to satisfy one's mind relative to certain
appearances, which we perceive going on externally. We have to form our
judgment of things we do not see from those that are apparent--at all
times a difficult task. But not often so tantalizing as in the case of
an insignificant creature like the Mussel, who lives, moves, and works
constantly before our eyes. I may add that it was not enough for me
that I saw the spinning process frequently. It all seemed tolerably
clear to my mind, but still I did not feel thoroughly satisfied. My
desire was to peep into the shell, and find out where the last spun
thread was situated; or, in other words, from what part of the trunk
the new branch sprung. On examining various specimens of the byssus,
this point was by no means apparent. Various means I adopted failed
to secure me the requisite knowledge. At length I hit upon a plan,
which, after no long time, I found opportunity to put in practice. My
largest Mussel lifted up its testaceous canopy, put aside the fringed
and fleshy veil that surrounded its edge, protruded its spinner to
make sure the ground was secure, and then withdrew it again into the
shell as usual. After the lapse of a second, the foot reappeared and
was stretched out to an unusual length. No sooner was the end of the
thread formed on the glass than immediately I firmly pressed the valves
together, and held them in this position until I had gradually worked
the Mussel up out of the vase, when I bound them close together by
means of a piece of cord. I need not describe my manœuvres further;
suffice it to say that the thread nearest to the base of the groove
was found to be the one that was spun last. This, in my opinion, is
invariably the case.
I may mention that the above experiment also proved to my mind that the
foot must be a most important vital organ of the Mytilus. At times, on
placing an open Mussel in my tank as food for crabs or other animals, I
have noted that if every other part were eaten, and the foot allowed to
remain attached to the muscles of the bivalve, that member would after
a lapse of several days show signs of--I do not say life--but sensation
and retractile power.
But when the foot is cut and otherwise injured, the animal dies
quickly. In the experiment mentioned the valves were not kept closed
for more than half an hour; yet when they were opened, vitality had
evidently ceased within. This was the more singular when we remember
that the Mytili will live for many days out of the water; the shells,
of course, during the whole period being firmly closed.
The Mussel, as already hinted, is very tenacious of life. I have kept
specimens by accident for several days in the pocket of my coat, but
found them quite well and lively when placed in sea-water.
In general the sure sign of their not being in a healthy condition is
when the shell opens; for, while the animal retains any sense whatever,
it exercises a strict and judicious 'closeness.'
I have found, however, on several occasions, that the shell being
contracted is not always a valid proof of its owner's convalescence,
for when placed in water the Mussel would float for several days upon
the surface like a cork, although it was near death's door.
This phenomenon must be caused, I should suppose, by some sudden fright
compelling the mollusc to close its shell with such rapidity as to
prevent a proper supply of water being taken in. Having only air to
exist upon, the animal then lingers on until its branchiæ become dried
up, and all moisture exhausted. In this state the Mussel opens its
shell with a deep bursting sigh, and sinks to the bottom--dead.
Being at the sea-side one fine summer day, I heard a little Scotch
girl cry out to her brother who was about to swallow entire, a fine
specimen of the _Mytilus edulis_, 'Eh, Willie dear, dinna ye eat that.
Dinna eat the _beard_ or ye'll dee!' Many years ago I remember a remark
to the same purport as the above being made by a poor child to its
playmate, in the neighbourhood of Gravesend.
I little thought at that time that the Mussel was so interesting a
shell-fish, or that I years after should spend many an anxious hour
studying the formation and nature of its despised beard.
I need hardly state that the idea of the beard being poisonous is a
vulgar error. In general the fish may be eaten entire with impunity.
Cases have occurred where persons have been taken ill after eating it,
but this result has been satisfactorily explained to have been caused
by the Mussels being procured from places such as Leith Docks, where
their food consisted chiefly of unwholesome and putrescent matters.
This mollusc is not used as food to any very great extent by the poorer
classes. It is employed very extensively, however, by the fishermen as
bait along all parts of the British coast. But in France it is much
esteemed both by rich and poor. The trade in them is successfully
cultivated, and affords a means of support to hundreds of industrious
and deserving men.
From the learned author of the "Rambles of a Naturalist" we learn
that at the village of Esnandes, on the coast of France, the Mussel
trade, commenced about eight hundred years ago, has assumed a gigantic
extent. Both here and at the neighbouring villages of Charron,
Marsilly, Mussels are bred in an ingenious and systematic manner. At
the level of the lowest tide short piles or stakes are driven into the
mud, in a series of rows about a yard apart. This palisade is then
roughly fenced in with long branches. On this structure the Mussel
spawn is deposited, and it is found that the molluscs thus produced in
the open sea are much finer than those which are bred nearer the shore.
These artificial Mussel beds are termed 'bouchots.' The fishermen who
engage in this branch of industry are known as 'boucholeurs.'
'The little Mussels,' continues M. Quatrefage, 'that appear in the
spring are known as _seeds_. They are scarcely larger than lentils,
till towards the end of May, but at this time they rapidly increase,
and in July they attain the size of a haricot bean. They then take
the name of _renouvelains_, and are fit for transplanting. For this
purpose they are detached from those _bouchots_, which are situated
at the lowest tide mark, and are then introduced into the pockets or
bags made of old nets, which are placed upon the fences that are not
quite so far advanced into the sea. The young Mussels spread themselves
all round the pockets, fixing themselves by means of those filaments
which naturalists designate by the name of byssus. In proportion as
they grow and become crowded together within the pockets, they are
cleared out and distributed over other poles lying somewhat nearer
to the shore, whilst the full-grown Mussels which are fit for sale
are planted on the _bouchots_ nearest the shore. It is from this part
of the Mussel bed that the fishermen reap their harvest, and every
day enormous quantities of freshly gathered Mussels are transported
in carts or on the backs of horses to La Rochelle and other places,
from whence they are sent as far as Tours, Limoges, and Bordeaux....
The following data, which were collected by M. D. Orbigny more than
twenty years ago, will show how important this branch of industry
must be to the district in which it is cultivated. In 1834 the three
communes of Esnandes, Charron, and Marsilly, representing a population
of 3000 souls, possessed 340 _bouchots_, the original cost of which
was valued by M. D. Orbigny at 696,660 francs; the annual expenses of
maintaining them amounted to 386,240 francs, including the interest of
the capital employed, and the cost of labour, which, however, is spared
to the proprietor who works on his own account. The nett revenue is
estimated at 364 francs for each _bouchot_, or 123,760 francs for the
three communes. Finally, the expense of the carts, horses, and boats,
employed in transporting the Mussels, then amounted annually to 510,000
francs; but these numbers are far from representing the expenses
or profits at the present day. At the time M. D. Orbigny lived at
Esnandes, the _bouchots_ were only arranged in four rows; now however,
there are _no less than seven rows, and some of them measure more than
1000 yards from the base to the summit_. The whole of these _bouchots_,
which were at first limited to the immediate neighbourhood of the three
villages, of which I have already spoken, extend at the present day
uninterruptedly from Marsilly far beyond Charron, and _form a gigantic
stockade for two miles and a half in breadth, and six miles in length_.'
A curious circumstance connected with the Mytilus remains to be
described. Let the reader, who may be so fortunate as to possess a
good microscope, cut away a portion of the fleshy part of the Mussel,
then place it in a watch glass, and examine it through that 'portal
to things invisible,' and, unless I am much mistaken, he will own the
sight to be supremely wonderful. Some water being deposited in the
glass the fleshy object will be seen to swim about in a most singular
and mysterious manner, while a close inspection shows every portion of
it to be in active motion.
This motive power is caused by countless cilia, the rapid vibration of
which creates constant currents. This action preserves the health of
the poor mollusc by ærating the water which passes over his respiratory
organs.
That some such wonderful contrivance is adopted, for conveying food
within the valves, too, is evident, when we consider that the Mussel
is always affixed to some foreign substance, that it cannot hunt after
prey, and therefore can subsist only upon whatever nutritious particles
may be contained in the element in which it lives. These consist of
minute animalculæ, principally crustacea, which are drawn within the
shell by powerful currents.
I have often watched this phenomenon through a hand lens, and have
seen the young shrimps and skip-jacks, for instance, notwithstanding
the nimbleness of their movements, irresistibly drawn into the gulf
of destruction. Even tolerably sized specimens that were seated in
fancied security upon a valve of the Mussel, have suddenly been drawn
in, out of sight. As an instance of the power of these currents, I may
state that the water in a small aquarium is often seen to be affected
by the respiratory action of a single bivalve. The same thing has even
been apparent to the writer, while watching the movements of a colony
of Barnacles attached to a Limpet, the most distant part of the fluid
being gradually drawn near, in obedience to the beck of these delicate
and graceful little creatures.