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The Cambridge Manuals of Science and

Literature

PEARLS

CAMBRIDGE UNIVERSITY PRESS
London: FETTER LANE, E.C.
C. F. CLAY, MANAGER

Evinburgh: too, PRINCES STREET
London: H. K. LEWIS, 136, GOWER STREET, W.C.
WILLIAM WESLEY AND SON, 28, ESSEX STREET, STRAND
Berlin: A. ASHER AND CO.
Leipsig: F. A. BROCKHAUS
$e Work: G. P. PUTNAM’S SONS
Bombay and Calcutta: MACMILLAN AND CO., Ltn.

All rights reserved

ro goo
ASN
So wi

W. J: DAKIN
Dise; FiL:S,

Professor of Biology
University of Western Awétralia

Cambridge : —
at the University Press

New York:

G. P. Putnam’s Sons

Canrbrivge :
PRINTED BY JOHN CLAY, M.A.

. AT THE UNIVERSITY PRESS

With the exception of the coat of arms at
the foot, the design on the title page is a
reproduction of one used by the earliest known
Cambridge printer, John Siberch, 1521

PREFACE

O one can be better aware of the defects in this

little book than the author. It has been
_written with a view to giving a summary of the most
important facts about pearls, pearl fishing and pearl
formation, and it is hoped by the writer that any sins
of omission will be pardoned. There is no lack of
literature on the subject of pearls, and some of the
volumes which have been published on this subject
are themselves of great value. They do not seem,
however, to be easily within reach of the average
reader, and they are nearly always written from
non-biological points of view. The works on pearl
formation are, on the other hand, usually very
technical. The structure and natural history of the
shell-fish in which pearls are produced are hardly
ever described outside scientific treatises; hence
the chapter on this subject. It seemed impossible,
to the author, to describe the processes of pearl
formation without reference to the structure of the
shell-fish. If it were only for common knowledge, a
description of the anatomy of a mollusc should be
interesting to the general reader, for very little idea
of the structure of even an edible oyster or mussel
seems to prevail. The book has been written by
a biologist, from the point of view of a biologist,

v1 PREFACE

and owes much to previous writers who have treated
the subject from other sides. To Professor Herd-
man, my former teacher, I owe very much, and his
descriptions of the Ceylon banks have been very
largely utilised. The writing up has only been
accomplished through the assistance rendered by
my wife, for by a curious coincidence it had to be
written under the stress and strain of preparations
for a removal to one of the countries referred to
on many occasions in the text, Western Australia.
Mr H. Jackson, M.Sc., has very kindly undertaken
the labour of proof reading ; without this help con-
siderable delay would have occurred in the publication.
To Mr Chambers, of University College, London,
I owe several interesting references to pearls in the
classics; and Dr Johnstone, of Liverpool, has read
certain parts of the manuscript.

If I have occasionally fallen into the pitfall of
becoming too technical, I trust that my readers will
turn to the glossary, and I earnestly hope that it will
help to clear up the difficulty.

W. 5

R.M.S. Mongolia,
Mediterranean.
February 1913.

CONTENTS

CHAP. PAGE
Er: THE HISTORY OF PEARLS. : : ; ‘ ’ 1
tL WHERE PEARLS ARE FOUND . : ; : : ll

Ill. THe ANATOMY OF THE PEARL OYSTER AND THE
STRUCTURE OF ITS SHELL : : ; : Le

IV. THE LIFE HISTORY OF THE PEARL OYSTER, AND

THE CONDITIONS UNDER WHICH IT LIVES ; 42
2 PEARLS . . : : : 2 ; : 2 52
VI. A CEYLON PEARL FISHERY . } : ; : 68
VII. PEARL FISHERIES OF OTHER LANDS , : ; 83
VIII. THE ORIGIN OF PEARLS . ; : : ; 91
1X. PEARLS IN JEWELLERY AND TRADE, ODD FACTS . 116
X. THE PEARL OYSTER, THE TRADER, AND THE
SCIENTIST . ‘ : : : : A : 124
BIBLIOGRAPHY . f : : : i . oS SS
GLOSSARY , : : ; : * : . 140

InpEX -. ‘ é é : : ; : : 144

FIG,

andy

LIST OF ILLUSTRATIONS

Valve of Ceylon pearl oyster
Section (diagrammatic) of molluscan shell
Nacre laminae in surface view

Anatomy of Ceylon pearl oyster

Positions of muscle pearls in Ceylon pearl oyster .

Section of pearl (prismatic)
Section of pearl (nacreous)

Nemertine worm imbedded in nacre

Diagrams showing formation of pearl in Mytilus .

Section of larval worm in Ceylon pearl oyster
Tetrarhynchus unionifactor

Diagrams of development of pearl sac

CHAPTER I
THE HISTORY OF PEARLS

THE use of pearls as jewels and their recognition
as objects of value date back into the far beyond
when the histories of ancient peoples were transcribed
upon papyrus. It is very likely that pearls were
amongst the earliest gems known to man, and this
is not surprising when one considers that the earliest
dwellers by the sea probably fed upon the shellfish
which produce such objects.

The modern recognition of the pearl dates back
to about 300 B.c. and was due, no doubt, to the mad
desire of the Romans for luxury and treasure ; but
although pearls seem to have played a less conspicuous
part in Ancient Greece and Egypt, they were known
to yet older peoples, and especially to those of the
East. The Old Testament only refers to pearls once,
in the book of Job (chap. xxviii), where it is written,
“No mention shall be made of coral, or of pearls; for
the price of wisdom is above rubies.” None of the
terms, however, refer with any certainty to the ob-
jects now known by such names. The names of gems

D. 1

2 PEARLS [cH.

in the scriptures have probably arisen during the
many translations and rewritings of the books.

In the New Testament, on the other hand, con-
stant reference is made to pearls. There are, how-
ever, traditions which refer to the ancient Hebrews
having knowledge of the true value of the gem.

In the Indian Seas pearls were known many
centuries before Christ. Perhaps first collected as
mere curiosities or as objects of some superstitious
regard, they gradually became articles of greater and
greater value, and the proud possessions of the Princes
of the East. References occur in the literature of
India which are of considerable antiquity. Pearls
are mentioned in the books of the Brahmans (about
500 B.C.) and are associated in Hindu literature with
Krishna.

The Chinese recor i: go still further back and
Kunz and Stevenson relate that a book, the Shu King
(2350—625 B.c.), states that in the 23rd century B.C.
Yii received as tribute, oyster pearls from the river
Hwai. The early Chinese pearls were evidently
taken from fresh-water molluscs.

The pearl fisheries of Ceylon and also of India

and the Persian Gulf, must be of very great antiquity,
but when and by whom discovered, are questions the
answers to which are buried in the annals of the
past. It is highly probable that the fishing was
carried on 2000 years ago, in much the same simple

1] THE HISTORY OF PEARLS 3

way as at present. The fishing of Ceylon was referred
to by Pliny, who stated that the island of Ceylon was
the most productive of pearls of all parts of the world.
According to Herdman the Singhalese records go
back still further, and quoting from his valuable
report—a mine of information about the fishing of
Ceylon—we read that “According to the ‘Mahawanso,’
pearls figure in the list of native products sent as a
present from King Vigaya of Ceylon to his Indian
father-in-law, in about 540—550 B.c.”; and again
when in Bc. 306 King Devanampiyabissa sent an
embassy to India the presents are said to have
included eight kinds of Ceylon pearls.

Pearls were almost certainly known to the Persians
seven centuries before Christ; they are not men-
tioned, but pearl ornaments of very great antiquity
have been found in Persian remains.

The ancient Egyptians used mother of pearl,
according to Kunz and Stevenson, as early as the
6th dynasty—3200 B.c., but they do not seem to have
regarded the pearl as being valuable until very much
later times.

As for the Greeks, they too knew the pearl and
recognised its value. The gems are mentioned in
the writings of Theophrastus and they are described
as being the products of shellfish. Pliny also refers
to the writings of the Greeks. Three centuries before
Christ a great change in the story seems to have

1—2

4 PEARLS [cH.

taken place. The Roman empire was beginning to
rise and very soon this mighty power became involved
in wars with those countries where the knowledge
of the pearl was general and its value as treasure
was recognised. By 50 B.c. the pearl had become
very popular in Rome. The Romans were indeed
strangely affected by pearls, and the gem was adopted
as a kind of fetish—a sign of pomp and luxury. The
value of the pearl became extraordinarily great and
laws were made forbidding the wearing of pearls by
individuals who had not attained to a certain rank.
Dresses were simply covered with the gem and even
animals wore necklaces. It is often said that the
presence of pearls in the molluscs of the rivers of
the British Islands, played some part in bringing
Julius Caesar to our shores. It is certain that in
those days the pearl was fished in England and in
this respect the following quotations are interesting :
From Caius Plinius Secundus.

In Britain, it is certain that small and badly coloured pearls are
found, since the Emperor Julius wished it to be understood that the
breastplate which he dedicated to Venus Genetrix in her temple was
made of British pearls. Lib. rx. 557.

From Caius Julius Solinus.

Dat et India margaritas, dat et litus Britannicum ; sicut divus
Julius thoracem, quem Veneri Genetrici in templum ejus dicavit, ex
Britannicis margaritis factum, subjecta inscriptione testatus est.
CFay Pie ie

From Tacitus,
Britain bears gold, silver and other metals as the reward of

1| THE HISTORY OF PEARLS 5

victory, the ocean also produces pearls, but dull coloured and dirty
brown. OC. C. Taciti de vitu Agricolae c. 5.

From Aelian.

The best [pearl] is the Indian, and that of the Red Sea. It is
produced also in the western ocean where lies the Brettanic island ;
but appears in a measure rather golden coloured having rays somewhat
dull and dusky. Juba says it is found also in the Gulf near the
Bosphorus, but that it is inferior to the Brettanic.

Aeliani de Natura Animalium lib. xv. c. 8.

From Origen.

But they hold the second rank, as among pearls, do those which
are taken from the ocean near Britain. They say that the pearl
obtained near Britain is golden coloured on its surface but cloudy
and rather dull in its rays; but that which is gotten from the Bay
near the Bosphorus is more cloudy than the Brettanic.

Orig. Comment. in Mattheum, Delarue t. 11. 448—50.

Most of the above writers seem to have regarded
the British pear] as inferior to the pearls of the Orient.
The Venerable Bede speaks more highly of the English
pearls, and writes :

“—among which are mussels in which they often
find enclosed pearls of all the best colours—that is,
both red and purple, jacynth and green, but principally
white.”

So did Britain in these times play its part in the
production of gems, which the makers of history
regarded as of first importance.

The Romans used the name margaritae (of the
Greeks), for pearls, but the term Unio was also
common in Rome. Pliny explains the term Unio

6 PEARLS [ CH.

as meaning that each pearl was unique, but other
theories have been put forward to explain this name.

After the fall of Rome and the scattering of its
treasures, we find that pearls once more become
objects of great value with the rise of another
conquering race. Byzantium or Constantinople
became the centre and capital of this new “Empire
of the East,” and with the development of life and
luxury arose the desire for adornment which was

even more gorgeous than that of the Romans. The.

treasures of Rome however had been scattered far
and wide and the pearl travelled far over Europe
even to the ancient cities of Gaul. Then we find
that as the Franks, too, became a prosperous and
conquering race under Charlemagne, the pearl again
came into great favour with the rich and powerful.
Later, when learning became the chief object in life
and books the greatest treasure, the pearl was chosen
to make beautiful the bindings of these books. Many
of them were most splendid and costly. One, the Ash-
burnham manuscript of the Four Gospels, which long
ago belonged to the Abbey of Canonesses on Lake
Constance, is now in the possession of Mr Pierpoint
Morgan. This MS. was bound about 896—899 A.D.
by order of the Emperor Arnulf of the Carolingian
dynasty, and according to Kunz and Stevenson has
98 pearls on it, all of which came probably from
rivers in Europe.

1| THE HISTORY OF PEARLS 7

After the 8th century, as the idea began to grow
that man was the centre of the universe,—that the
world was made for man,—a new use was found for
pearls. It was thought that all things which grew
naturally, were of direct use in helping to keep the
body sound and healthy. Hence we find that many
of our common herbs and lowly plants came to be
used as medicine, and they were used for whatever
their shape or colour suggested. So we get the
origin of the “kidney” bean, and the “liver ’-wort.
The pearl seemed so beautiful and pure that the
idea arose that it too must be of some value in this
respect. So we find that the small seed pearls were
used as medicine, sometimes ground into powder,
sometimes swallowed whole.

It was not until about the 12th century that
pearls were used in England, for the Anglo-Saxons
were not artistic, in the lavish manner of more south-
ern races. All through the 13th and 14th centuries
pearls were extremely fashionable over the whole of
Europe as ornaments for both men and women.
They were conspicuous too in church decoration, so
that from the spoil which Henry VIII obtained when
many of the churches were plundered, he came into
possession of numerous and costly pearls.

During the 15th and 16th centuries, pearls came
into still greater favour than before. Many of the
German cities revived the old restrictions of the

8 PEARLS [ CH.

Romans and no maiden or married woman was
allowed to wear the gem ; later they were restricted
to one pearl chaplet. There were many laws and
regulations as to their use by knights, the most
stringent being in Venice.

It was not only by the inhabitants of the Old
World that pearls were discovered, for Columbus
found that pearl fishing was carried on in the Gulf
of Mexico, and quantities of pearls have been found
in the Indian mounds, either loose or strung for neck-
laces and wristlets. Some were mounted in quaint
and primitive fashion, all showing that in the days
of swarming game and roving tribes of untrammelled
savages, their queens wore pearls even as they are
now worn by their fair successors. The old Spanish
traders obtained pearls, by fair means and foul, from
the ancient treasures of the Aztec kings. America
was even known in Cadiz as the “Land of Pearls,”
and the gem is still fished in the Caribbean Sea,
along the West Coast of Central America, and on
the Pearl Islands in the Bay of Panama.

It is surprising how little was known in the very
ancient days about the pearl-producing shellfish, when
the pear] itself was known so well. The gems were
thought by the Incas to be the “eggs” of the animal.
In the time of Alexander, a writer of Mytilene in the
island of Lesbos, says “In the Indian sea, off the
coasts of Armenia, Persia, Susiana and Babylonia,

————————— Oe =

1| THE HISTORY OF PEARLS 9

a fish like an oyster is caught, from the flesh of which
men pick out white bones, called by them ‘pearls.’ ”

In Britain the most important pearl fishing was
carried on in Scotland. As early as 1355 a.D. Scotch
pearls are referred to in a Statute of the goldsmiths
of Paris. In the reign of Charles II the pearl trade
was sufficiently important to attract the attention of
Parliament, and for many years a large number of
pearls were “cultivated.”

In 1705, we find a pearl merchant named John
Spruel saying that he had been dealing in pearls for
forty years but could never sell Scotch pearls in
Scotland, he could only sell oriental specimens. The
latter were always preferred although he could show
much harder and better Scotch specimens. (This
appears in an account current betwixt Scotland and
England, Edinburgh 1705.) In 1860 the Scottish
pearl fishery was revived by a German named Moritz
Unger. He visited Scotland and bought pearls from
the peasants. This resulted in a vigorous search for
the gems, and in 1865 we find that the total value
of the pearls sold was about £1,200. This price,
however, was not maintained, as the rivers were
over-fished. Now, pearls are only found irregularly
in the Spey, Tay, and South Esk, and to a less extent
in the Doon, Dee, Don and Forth.

Pearls have also been found in Wales, chiefly
in molluscs taken from the river Conway. One

10 PEARLS [CH.

of these Conway pearls was given to the queen
of Charles II by her chamberlain, Sir Richard
Wynn. The specimen is now believed to occupy
a place in the British regalia.

During the whole of the 18th century pearls were
somewhat scarce, both the Ceylon and Red Sea
fisheries being unproductive. The most plentiful
supplies came from the Persian Gulf and from fresh-
water shellfish. At this period, however, diamonds
became fashionable owing to the discovery of new
methods of cutting and preparing them. In spite
of this rival, the pearl] still continued in favour and
by the end of the 19th century it was more sought
after and more valuable than ever.

During this century there were discoveries of
pearl banks off newly settled countries, as for
example, Australia, and in this country they became
one of the sources of wealth to the colonists. The
growing value of the pearl is not due therefore to
a decrease in the source of supply but to an ever-
increasing demand for a gem which never seems out
of place for personal adornment or in any scheme of
decoration.

It | WHERE PEARLS ARE FOUND 1p

CHAPTER II
WHERE PEARLS ARE FOUND

PEARLS are found in the soft parts of aquatic
animals known scientifically as molluscs, and
popularly as shellfish. Inasmuch, however, as our
English Board of Agriculture and Fisheries lists
together such creatures as shrimps, periwinkles,
crabs, lobsters and oysters as shellfish, it will be
advisable, for our purpose, to use the much more
correct term, Mollusca. The molluscs are known to
everyone by their shells, but to very few by the
much more important part—the animal that made
the shell. The shell is merely an external covering,
a.secretion of the outer layer of the animal’s body—
of the animal’s “skin,” to speak popularly. Now
if we were to try and enumerate the molluscs in
which pearls occur we should probably have to give
the names of almost all the bivalves. There is no
reason why the sequence of events which produce
pearls in one species should not occur, if not regu-
larly, at odd intervals in other species. Not all pearls
however are valuabie. Most of these structures are
dull and worthless. We shall therefore turn our
attention to those molluscs in which are found

12 PEARLS [CH.

pearls having some resemblance to the gems of that
name, or which have played some important part in
the scientific investigation of pearl formation.

First and foremost mention must be made of the
Ceylon Pearl Oyster. The name oyster, however, is
here altogether a misnomer. The pearl oyster is
more closely related to our common edible mussel
than to our edible oyster. The Ceylon pearl oyster
(Margaritifera vulgaris) is not very large, the adult
of about three and a half years of age measuring, on
an average, about 7 by 6°5 centimetres.

Margaritifera vulgaris occurs, in addition to the
Ceylonese waters, in the Persian Gulf, the Red Sea,
near the Maldive Islands (where however it does not
appear to be fished for pearls), Kast Africa, and the
Malay Peninsula. It is interesting to note that since
the opening of the Suez Canal this pear] oyster has
migrated into the Mediterranean from the Red Sea.
The pearls found in this species vary somewhat in
beauty according to the district in which the mollusc
occurs.

Next to the Ceylon pearl oyster, mention must
be made of other species of the same marine genus
Margaritifera which are fished for pearls, or for their
shells, if these are valuable enough for the mother-of-
pearl industry.

The most valuable, and at the same time the
largest, mother-of-pearl oyster, is Margaritifera

11 | WHERE PEARLS ARE FOUND 13

maxima, Jameson, which occurs on the north coast
of Australia. Its distribution extends also down the
west and east coasts for some distance. These shells
are the “Port Darwin” shells, the “ Queensland ”
shells, and “West Australia” shells of commerce.
This species is also found off the coasts of New
Guinea (where it is called the “New Guinea” shell),
in the Malay Archipelago, and at the Philippines ;
these Philippine shells being known as “Manila”
shells.

Another very important species is Margaritifera
margaritifera which occurs with several varieties in
the trade. One variety is found off the north coast
of Australia with extensions down the east and west
coasts of that continent. This is the variety known
as the Australian “ Black-lip.” It also occurs in the
Malay Archipelago with extensions to Ceylon and
the Maldives. Another variety is fished at Zanzibar
and Madagascar, and is known for trade purposes as
the “Zanzibar shell.” The variety persica, fished in
the Persian Gulf and shipped from Bombay, is the
“Bombay shell” of commerce. The variety ery-
thraeensis, Jameson, is the “ Egyptian shell” of the
trade, and is fished at Aden and other places. From
Panama comes the “Panama” shell, which is the
variety barbata. Other varieties include the “ Poly-
nesian shells,” “Gambier shells,” “Tahite Black-lip,”
and the “New Guinea Black-lip.”

14 PEARLS [cH.

Of the many other species! of Margaritifera it
will perhaps suffice to mention the “Sharks Bay
shell,’ which is fished at Sharks Bay, Western Australia,
and plays an important part in the button industry.

Fresh-water molluscs in which pearls are found
include many famous species belonging to the family
Unionidae in the rivers of the British Islands.
Margaritana margaritifera, Linné, occurs in the
rivers of Scotland, northern England, Wales, and
the mountainous parts of Ireland. °

It is from this shell that the valuable fresh-water
pearls have been obtained. The shell is thick, and is
oblong in shape with both ends obtusely rounded.
The surface is rough and dark brown in appearance.
It is between five and six inches long.

The Romans came to Britain for the Undo pearls
and there is some evidence to show that they fished
the Welsh rivers for them. Many valuable pearls
have also been taken from Unio in Scotland, and
an important Scotch pearl fishery was once in
existence on the Tay in Perthshire. The Irish pearl
mussels seem to have decreased in number—perhaps
owing to the wanton destruction which has occurred
owing to the search for pearls. Pearl mussels occur
in the rivers of Central Europe, and America (both
Canada and the United States).

1 For a complete list reference should be made to Jameson, Proc.
Zool. Soc., 1901.

11 | WHERE PEARLS ARE FOUND 15

Pearls occur in Anodonta, a large bivalve, common
in many of our English ponds and lakes. The pearls
from this mollusc provided material for the work of
Home and Filippi (1826 and 1852), on the origin of
pearls. In Chinese rivers and lakes an allied genus—
Dipsas, is of great importance commercially, and has
been cultivated in enclosed waters. It is in this shell-
fish that the Chinese insert little images of Buddha
or some other deity, which are eventually coated over
with mother of pearl.

A considerable fishery for fresh-water pearls is
carried on in the rivers of the United States of
America. In fact this fishery is much more important
than that of Europe. It dates back some considerable
time before the white people took possession of the
countries of the West. One of the most recent and
greatest fisheries was that in the State of Arkansas
in 1897. The genera of shellfish (which are again
members of the family Unionidae) include Quadrala,
Pleurobena, Lampsilis and Tritigonia.

Pearls occur very frequently in the common edible
mussel (Mytilus edulis) of our sea coasts, and especially
in those from certain areas. Numbers up to twenty-
six often occur in a single mussel, and Johnstone and
Scott, on one occasion at Piel, obtained 390 pearls
from sixty-one mussels examined. Lest anyone should
imagine that a gold mine exists in the shape of pearls
in our mussel beds, we must add that the greatest

16 PEARLS [cH.

value of these pearls is as material for scientific in-
vestigation. The “gems” are usually dark and dirty
in colour and possess little, if any, lustre. The common
edible oyster has also been found to contain pearls,
and stories are current of fortunate individuals who
have found them when on the point of devouring
this esteemed shellfish. It is probable that the part
of the story dealing with the value of the pearls
contains gross exaggerations !

Another interesting mollusc in which pearls have
been found, and which was at one time much more
valuable than at present, is Haliotes—the Ear Shell.
It is probably familiar, in appearance if not by name,
to all readers of this book. The shell occurs in large
numbers in the English Channel on the rocky shores
of the Channel Islands. The exterior is a very dull
dirty brown—rough and coarse in texture. A series
of holes perforate the shell near one side. The internal
surface is lined with most beautifully coloured nacre.
In fact the play of colours is probably equalled in no
other shell.

This mollusc is called the “Ormer” in the Channel
Islands, and the “Abalone” in America. It will be
seen that the genus has a wide distribution and as
a matter of fact it has been fished on the coasts of
China, Japan, California, South Africa and New
Zealand. The shellfish is not a bivalve. There is
only one valve, and it covers the animal, which

11] WHERE PEARLS ARE FOUND 17

adheres to the rocks by means of a muscular foot
just as its relation, the common limpet, does. The
shell has been used largely in decorations, as electric
light shades, etc. but does not seem much sought
after at present. The inhabitants of the Channel
Islands sometimes use it to decorate the exterior of
their houses.

Finally, as a representative of quite another group
of molluscs, that to which the cuttlefishes belong, we
must add that pearls are found in the pearl Nautilus
of the tropics.

This list is by no means an exhaustive one but it
will serve to indicate some of the shellfish in which
pearls occur and the countries in which they are to
be found.

CHAPTER III

THE ANATOMY OF THE PEARL OYSTER MARGARI-
TIFERA VULGARIS, SCHUM., AND THE STRUCTURE
OF ITS SHELL

A SIMPLE account of the anatomy and biology of
the Ceylon pearl oyster is interesting and necessary
to any who would follow further the romance of
pearl formation.

D.

bo

18 PEARLS [CH. III

The oyster of Ceylon belongs to a group of
molluscs known popularly as_ bivalves, but more
scientifically as Lamellibranchiata. This name re--
fers to the characteristic plate-like gills. The group
includes the well-known edible oyster, the edible
mussel, cockle, and almost all the other shellfish
which produce pearls. The Ceylon pearl oyster is
a near ally of the scallop, a lamellibranch caught
in large quantities at many places round the British
Islands and enjoyed as a luxury by the few who have
recognised its delicate flavour. The degree of re-
lationship between the scallops and the Ceylon pearl
oyster is, as a matter of fact, much closer than that
between the latter and our edible oyster.

The soft body of the animal is enclosed between
two valves of shell which are hinged together along
a line which is dorsal in relation to the body. The
opposite edges of the valves, at the shell opening, are
therefore ventral and each valve is situated laterally
on the creature’s body—that is, there is a right and
a left valve.

Each valve is rounded in outline, but the dorsal
edge or hinge is flattened and ends in wings (or
auricles) in front and behind.

The shell of a four-year-old oyster measures
about 9°0 cm. from the hinge-line to the opposite
ventral edge and about 8°5 cm. across the valves.
The shell is not thick like that of the edible oyster or

Fig. 1. Inner surface of valve of Ceylon pearl oyster (Margaritifera
maxima).

20 PEARLS [CH.

the mother-of-pearl oysters, but very thin (only about
1°5 mm. in thickness), and it is lined by the usual
nacreous layer, or mother-of-pearl, which is here
exceedingly brilliant and iridescent. The mother-
of-pearl layer does not extend to the edge of the
valve and consequently the margin is still thinner.
It is only composed of two layers, which will be
referred to below. The external surface of the shell
is rough and dull in colour and usually obscured by
various other organisms growing upon it.

The hinge-line is a ridge which runs along the
dorsal edge of each valve. Close to it and extending
for about the middle third of its length is a tough
black elastic ligament. This ligament, compressed
when the two valves are closed, is thus always tending
to divaricate the valves and open the shell. Itis a
dead material and consequently unaffected by the
action of the animal. Inside the two valves, however,
is a powerful muscle (the adductor, fig. 4) which is
attached subcentrally, and this serves to close the
shell. The shell valves are thus pulled together by
muscular action, but they open automatically when
the muscle is relaxed by virtue of the elastic liga-
ment. For this reason the shells gape when the
animal dies.

The shell of most molluscs, and practically all
bivalves, like the pearl oyster and the fresh-water
mussels, is composed of three layers, but a fourth

111] THE PEARL OYSTER 21

occurs at places where the closing (or adductor)
muscles are attached. It will be necessary to describe
these layers in some detail, for the same structures
are present in pearls. In fact, pearl structure is very
similar to shell structure.

The outermost layer of the shell is known as the
Pervostracum (see fig. 2). It is a more or less horny
layer which is normally secreted by the cells of the

Fig. 2. Diagram of section of a typical molluscan shell. P, Peri-
ostracum. Pris., Prismatic layer. Nac., Nacreous layer.
H, Hypostracum.

‘edge of the mantle only. Consequently it does not
increase in thickness after once it has been formed.
In young shellfish the periostracum is relatively much
thicker than in old specimens, for the other layers
increase in thickness. Very often, too, the peri-
ostracum is really thinner in the adults, because it
gets rubbed off.

The periostracum is sometimes continued in the
form of numerous lamellae, into the next deeper

29 PEARLS [cH.:

layer of shell substance. This layer is known as the
Prismatic layer. It is of much greater thickness
than the periostracum, and is built up of calcareous
columns or prisms arranged at right-angles to the
surface of the shell. The prismatic layer, just like
the rest of the calcareous shell, consists of both
inorganic and organic substances. The organic part
forms a kind of framework upon which the calcium
carbonate is deposited ; the organic substance itself
is known as conchyolin.

The prismatic layer also is secreted normally by
the cells of the mantle edge only. It cannot increase
in thickness after it has once been formed. The
prisms of which it is built are often surrounded by
very delicate sheaths of periostracal-like substance
and each prism or column is transversely striped.
In fact, each column looks like a little pile of
microscopic coins. This prismatic layer often occurs
in pearls.

The third layer to be referred to is the most
important of all from our point of view. It is the
innermost layer, forming the internal surface of the
shell, except at the small areas where the adductor
muscle is attached and where there is a still more
internal layer of shell substance.

It is known as the nacreous layer, and consists of
that valuable substance, mother-of-pearl.

The nacreous layer differs from the layers already

ee

111 | THE PEARL OYSTER 23

described in being secreted normally by the entire
external surface of the mantle. Consequently, it can
increase in thickness throughout the life of the
animal. It is built up of very delicate lamellae or
tiny platelets which are arranged overlapping one
another (fig. 3), parallel to the surface of the shell.
The edges of the lamellae are zigzag, and as the sur-
face of the mother-of-pearl layer exhibits parts of the
faces and also the edges of the lamellae, a surface is

Fig. 3. Nacre or Mother-of-Pearl laminae in surface view
(highly magnified).

formed which possesses by virtue of interference
phenomena the so much-desired iridescent lustre.

It is this nacreous layer which gives the pearls
their beauty, and it is this layer which is often
deposited over sand grains, or objects placed by man
between the shell and mantle. Further reference to
the nacreous layer will be made later.

The last layer to which reference will be made
here is found between the muscle and shell. It is

24 PEARLS [CH.

called the Hypostracum, and is, like the two preceding
layers, formed of calcium carbonate. It is built up
of distinct columns arranged at i indiniet to the
surface of the shell.

Now let us briefly look at the course of shell
growth. The shell grows in size at the edge. Here
the edge of the mantle is forming periostracum and
prismatic layers, and there is practically nothing else.
A little distance in from the edge of the shell the
surface of the mantle is secreting nacreous or mother-
of-pearl substance, and this goes on continually.
Thus the shell increases in thickness over its whole
inner surface.

The secretion of the shell is really very compli-
cated, though the organs forming it may appear very
simple. Shell formation is due entirely to the cells
covering the mantle. These cells fabricate and pour
out (or secrete) a mixture of organic and inorganic
substances (conchyolin and lime). Crystallisation of
these substances takes place altogether outside the
animal and the shell is the product.

What determines the regularity of structure or
the formation of beautifully marked or sculptured
shells is unknown. All the cells seem practically —
alike, yet there must be some determining factor
hidden there. If a mollusc shell is broken (or a
piece of the shell is removed) some distance away
from the edge, a most extraordinary thing happens

IIT] THE PEARL OYSTER 25

which is of the greatest importance in regard to
theories of pearl formation.

The shell is repaired, but the repair substance is
not, as was once thought, only nacre. The mantle
cells, which normally would be secreting nacre, now
secrete at the area of breakage, first periostracum,
then prismatic layer, and finally mother-of-pearl.

Thus, although certain parts of the mantle surface
secrete normally certain definite parts of the shell,
the cells which secrete the nacre are capable of
secreting all the other layers if necessary. This
extraordinary property is made use of in the
formation of pearls, as will be seen later.

Let us now leave the dead shelly covering and
look at the animal itself which has been responsible
for the secretion of the valves. The figure (fig. 4)
is a view of the right side of the animal. In the
centre there is to be seen the large adductor muscle,
and this seems to take the place of a central scaf-
fold. Dorsal to this, that is towards the hinge-line,
is a soft unsegmented body in which lies the heart
and the viscera. Ventral to the muscle are the
flat plate-like gills hanging down as curtains into
the cavity that is enclosed by the two valves. On
the left the foot is to be seen with fibres of byssus.
The mouth is situated above the byssus. This figure,
with the rough description given above, represents
what is seen when a flap of tissue (very important, as

26 PEARLS (CH.

we shall see, from the point of view of pearls) has
been removed. This flap, known as the mantle or
pallium, is a lateral fold of the wall of the body of
the animal. It is similar in shape to the valve of
the shell; in fact it has formed the latter.

The cavity between the two mantle flaps into
which one looks when a mollusc’s shell is opened,
is of course nothing else but part of the external
world, and is known as the pallial cavity. The sea-
water enters this space and bathes the gills which
hang down into it and also the internal faces of
the mantle flaps. The mantle lobes are therefore
separated anteriorly, ventrally and posteriorly, but
continuous dorsally underneath the hinge-line. The
free edge of the mantle is thickened and darker in
colour than the rest. It also bears numerous short
tentacles. In the common scallop the mantle edge
bears numerous complex eyes as well as the
tentacles.

It is usual to find the edge of the mantle thickened
very considerably in the majority of bivalves, and, as
we have seen, the edge is of great importance, for it
secretes tivo of the layers of the shell, the external
periostracum and the prismatic layer. These two
layers are renewed by the mantle edge, and growth
of the shell, so far as these layers are concerned, can
only take place at the margin.

The inner nacreous layer is, on the other hand,

111 | THE PEARL OYSTER 27

secreted by the whole face of the mantle in contact
with the shell.

The mantle itself is formed of connective tissue
with numerous blood spaces—it has an extensive
blood supply. It is bounded by a layer of cells, the
ectoderm, and the ectodermal cells, next to the shell,
are secretory, as we have seen. The ectoderm facing
the pallial cavity is ciliated, that is, the cells possess
delicate vibratile processes or “ cilia.”

The Foot is an organ capable of very consider-
able expansion and contraction. It arises from the
visceral mass just below the mouth.

The variation in size is brought about in the
following manner. The foot is highly muscular, but
it is also full of cavities which communicate with the
blood system. If blood is forced into the spaces the
foot increases in size and becomes several times as
large as in the contracted condition. Contraction
takes place by muscular action. It is by alternate
expansion and contraction in this way that the
common razor shell of our coasts bores its way down
into the sand.

On the ventral surface of the foot and at the end
nearest the body is a gland, situated ina pit. From
this a groove runs to the end of the foot to another
pit. The gland secretes the fibres known as byssus,
easily seen in the common edible mussel, and in both
cases the byssus is used for attaching the animal to

28 PEARLS [ CH.

the rocks or to other shells. All these structures
are indicated in fig. 4. In addition, however, to the
secretion of byssus and its attachment by the same,
the foot is actually used for locomotion.

Ligament stomach Digestive Gland
Mouth

Foot

ee Byssus
g Strands
Byssal

Groove \

Rectum

Anus
Adductor-#°*S er
Muscle Se:

Fig. 4. Ceylon Pearl Oyster. Mantle and gills from one side
removed. (After Herdman.)

The byssus can be pulled away, and then the
pearl oyster, being free, extends the foot and uses it
as a crawling organ in a somewhat similar manner to
the snail. Having found perhaps a more suitable

EEE ee ee

UT] THE PEARL OYSTER 29

position for re-attachment, the top of the foot 1s
applied to some rock, and the pit at the end of the
byssal groove is thus pressed against the attachment
surface. The edges of the groove are now brought
together, so that a narrow tube is formed, and down
this tube passes a fluid secretion from the byssal
gland.

It soon hardens in contact with sea-water, and
after about five minutes the foot may be withdrawn
from the attachment surface. It will then be seen that
an elastic fibre extends from the mouth of the byssus
gland pit to the point where the other pit was pressed
against the rock. This process is repeated very many
times, until a large number of fibres extend in a
bunch from the byssus gland opening to the attach-
ment surface.

If a pearl oyster or an edible mussel is pulled
away with force from its attachment, the byssus is
not usually detached from the foot. It comes away
from the rock or it breaks. After some time, how-
ever, the mollusc sheds the old byssus, and if it
re-attaches itself it does so by the secretion of a new
one.

The Muscles.
Reference has already been made to the large

central adductor muscle which pulls the two valves
together and closes the shell. In many of our

30 PEARLS Tort

bivalves there are two adductor muscles. Where
one only is present, it corresponds to the posterior
of the two. This adductor muscle can contract with
considerable force. The force required to open an
edible oyster, an edible mussel or a cockle is probably
known to most readers. This force is being ex-
pended in overcoming the strength of the adductor
muscles. Whilst, however, the bivalves can resist
very considerable pulls made for a short period, a
very weak pull is sufficient, if sustained for some
time, to break down the oyster’s protection. This is
the cause of much trouble, for one of the enemies of
the bivalve, the starfish, opens the shell merely by
pulling on both valves with comparatively little force,
but with an insistence that is to be admired. The
process is interesting, because for a long time it was
supposed that the starfish poisoned the mollusc, when
of course after death the shell would open auto-
matically. This is not the case, as the starfish
simply applies its arms to the two valves of the shell,
attaches its numerous “ tube feet” and steadily pulls.
When its perseverance has been rewarded by the
divarication of the two valves, the stomach is ex-
truded and the animal proper of the mollusc digested.

In addition to the adductor muscle, there are
several other large and definite muscles which are
connected with the foot.

There are six of these altogether. All are

111 | THE PEARL OYSTER 31

attached or inserted on to the shell valves. Two of
them are known as Retractors. They originate in
the walls of the byssus gland and pass backwards one
to each shell valve. The other four are Levators,
two of which are anterior and two posterior. By the
contraction of these muscles the foot is moved from
side to side or retracted.

The protrusion of the foot to the outside of the
shell is produced by a rush of blood into the cavities
of this organ.

There are numerous other smaller and diffuse
muscles in the body which need not be detailed.

The Viscera.

There is no large cavity in the molluscs which,
like the human body-cavity or coelom, apparently
contains the viscera. The cavity which corresponds
to this is small; it is termed the pericardium, and
contains the heart. As in all bivalves there is a
definite heart with blood vessels, but the vessels often
expand into mere cavities in the tissues and it is
difficult to speak of arteries and veins, except when
referring to definite large vessels with cellular walls.

The heart, in the pericardium, is situated dorsal
to the adductor muscle and between it and the so-
called liver (see fig. 4).

Themouth of the animal is situated high up near the
hinge-line, above the foot and consequently anterior

32 PEARLS [cH.

in position. It is partially hidden by two lips which
are produced at the sides to form flat plates—known as
labial palps. Since each corner of the mouth is
produced laterally to merge into the gutter between
the two palps on each side (a feature not easily
shown in a diagram), the two pair of palps act as
directing walls and guide food to the mouth. The
mouth leads into the alimentary canal, a more or less
simple tube, which, with the exception of a swollen
region, the stomach, is much the same in structure
and appearance throughout its length.

It coils once and finally runs over the adductor
muscle to open by the anus into the cavity between
the two shell valves. The stomach is embedded in,
and surrounded by, the so-called liver. It is very
difficult, however, to compare any organ in Inverte-
brates with organs in Vertebrates, and this so-called
liver possesses many functions that are not performed
by the human liver. It is better to call it a digestive
gland. It secretes juices that help to break up and
alter the food and it absorbs this digested nutriment.

Now let us see how these organs do their work
and by what means the pearl oyster obtains its food.
Starting at the very beginning of the story, the food
of the pearl oyster consists of minute animals and
plants which occur everywhere floating in the sea-
water. These same microscopic organisms are found
in the fresh water of ponds, streams, rivers and lakes

111] THE PEARL OYSTER BT,

—and they occur in the sea, though of course different
species are characteristic of all these different
situations and are in fact characteristic and different
for each season of the year.

These organisms must be brought within the
shell, and as the bivalves are not capable of pursuing
them, a current of water is caused to flow into the
shell cavity which will bring them with it. This
current of water is very important for another reason
—the pearl oyster, like other living organisms, must
breathe. It obtains its oxygen from the water, and
consequently a current of water must enter the shell
continually, bringing in oxygen, and must pass out
again with carbonic acid gas, the product of re-
spiration.

Thus an inflowing current of sea-water brings
oxygen for respiration and food for nutrition at the
same time. The water current is produced chiefly
by the gills. We have already referred to these
organs as being flat plates in the bivalve molluscs.
They occur as two double plates on each side, hanging
down like curtains from the adductor muscle and
visceral mass, and occupying a considerable part of
that cavity (itself a part of the external world) which
is encompassed by the two valves of the shell. These
are really only two gills, but as each one appears as
two double plates (half gills) there are often said to
be four. It must be remembered then that each one

D. 3

34 PEARLS [CH.

of the four is butahalf gill. Two half gills belong to
each side of the body.

Each gill plate is made up of a number of
filaments, all hanging down side by side. They are
held together by delicate hair-like processes, so that
they appear to make up a firm sickle-shaped plate.
As a matter of fact, a slight touch with the finger
serves to separate the filaments so that a gill plate
looks like a comb, the teeth of which are not brittle
and strong, but soft, and only kept in position by
adhering to one another. Perhaps a better com-
parison would be with the vane of a feather. Here
also we have a number of delicate processes which
are held together to form a flat plate.

The gills are covered with delicate microscopic
hair-like processes or cilia, arranged in a regular and
particular manner, and it is by the continual wafting
of these cilia that the water current enters the shell.
Probably all readers of this book have watched the
effect of the wind, blowing across a field of corn.
Successive waves appear to cross the field, but the
motion of each cornstalk is to and fro. If one could
make the cornstalks move in this way, of their
own accord, the process would be reversed and a
current of air would be produced. This is exactly
what takes place on the gills: the cilia are the
individual cornstalks—they move continually, but
rhythmically one after the other, so that waves are

nT] THE PEARL OYSTER 35

set up. This sets the water in motion. The current
of water enters the shell between the two mantle
lobes at a region about the middle of the ventral
margin. It passes over the gill plates and through
them. Passing through them continually, the water
is to a certain extent robbed of its oxygen and leaves
the shell at what is known as the exhalent opening,
situated posteriorly. If however food particles enter
with the water of the inflowing current, they are
wafted along the gill margins anteriorly, until they
reach the two flaps known as the palps. There are a
pair of these on each side of the body; the outer-
most of each is really a prolongation of the upper lip
of the mouth and the innermost a prolongation of
the lower lip. Consequently the gutter or groove
between either pair of palps leads to the mouth.
Like the gills, the palps are covered with cilia,
hence the food particles are wafted along between
them up to the mouth opening. The particles may
be accepted as food (and then they pass into the
alimentary canal) or they may be rejected. In the
latter case they are picked up by a current of water
running along parallel and close to the margin of the
mantle and are carried back until the exhalent
opening is reached. Here they leave the shell
together with the current of water that has passed
through the gills. In this manner the pearl oysters,
and indeed also the cockle, mussel, and other bivalves

3—2

36 PEARLS [CH.

obtain their food. They search not, neither do they
place food in their mouths by special appendages.

Reference has been made once or twice to the
gills. It must be said here that they are not the only
organs concerned in respiration.

The mantle lobes themselves are very efficient
respiratory organs, for they contain numerous blood
spaces, and the wall separating this blood from the
sea-water in the cavity of the shell is extremely thin
and allows the interchange of the gases.

The Blood System.

All bivalves possess a heart and system of blood
vessels. This perhaps is not common knowledge,
because the blood of these molluscs is practically
always colourless. The absence of the characteristic
red haemoglobin of human‘blood does not render the
blood different so far as function is concerned. There
are other chemical compounds present instead, which
help to carry out chemical changes similar to those
performed by haemoglobin in human respiration.

The heart consists of one ventricle, a central,
dorsally situated, muscular-walled bag, and two
auricles, one on either side, with much thinner walls.
The ventricle contracts or “ beats ” rhythmically, and
at each contraction the contained blood is forced
out through two arteries (not shown in fig. 4) to the

It | THE PEARL OYSTER 37

system. On dilatation after each contraction, blood
is sucked into the ventricle from the auricles. The
blood can only flow in one direction. Itis prevented
from re-entering the auricles, when the ventricle
contracts, by valves which guard the orifices. The
auricles receive their blood from the gills and mantle ;
thus the heart only contains blood of one kind—pure.
The blood system is much more simple than that of
man, where the heart has two ventricles, and pumps
out both pure and impure blood.

The Excretory Organs.

The pearl oyster possesses two so-called “kidneys.”
They are simply tubes which open at one end into
the pericardium and at the other into that part of
the external world enclosed by the two shell valves.

Excrete matter is removed from the blood, which
circulates in the walls of these tubes and is passed
into the lumen, eventually reaching the exterior.
Waste matter may also be excreted into the peri-
cardium itself by the walls of the heart. This excrete
matter also passes down the lumen of the kidneys to
the exterior.

There now remains to be described the nervous
system and sense organs, and finally the reproductive
organs to render this general account of the anatomy
complete.

38 PEARLS [cH.

The Nervous System and Sense Organs.

Since bivalves like the pearl oyster and the mussel
do not make a very active search for food, but lead
a sluggish existence, partaking of such nutriment as
is wafted to them, they miss that active struggle for
existence which is bound up with a search for food
and a combat with enemies. Not that they take no
part in a struggle for existence. That seems to be
part of the ordained law of life for every organism.
It is here, however, more of a passive nature. We
are not surprised then to find that both nervous
system and sense organs are but simple.

Here in fact is the explanation of the absence of
a definite and obvious head with eyes and other
organs. To the man in the street an animal lacks all
individuality if it does not possess such a structure,
on which he may interpret some expression. One
cannot point to the animal’s head, but merely to the
head region. Specialised sense organs are few, and
they cannot be compared to any possessed by well-
known vertebrate animals. They are of use to the
animal for orientating itself and for testing the water
which continually streams into the shell. The edges
of the mantle are sensitive to light, and a shadow
thrown on to them causes an immediate closure of
the shell. This is the sole means of defence pos-
sessed by the pearl oyster. As a matter of fact,

ur] THE PEARL OYSTER 39

when eyes are present in the bivalves they are
usually situated, not in the head region, but on the
mantle edges, the only regions where they would be
of any service. Thus do necessity and use triumph
in nature over all else.

The nervous system consists simply of three pairs
of small bodies or ganglia (which are aggregations of
nerve cells) connected by nerve fibres. One pair, the
cerebral ganglia, is situated in the head region at the
sides of the oesophagus. Another pair, the pedal
ganglia, is connected to the cerebral ganglia by two
connectives, but the two ganglia are fused to form
one mass at the base of the foot. The third pair
is situated on the face of the adductor muscle. The
ganglia of this pair are connected to the cerebral
ganglia but not to the pedal.

Thus the nervous system is bilaterally symmetrical
and composed of right and left halves.

In this simple invertebrate nervous system we
find nerve fibres running out from these ganglia to
muscles. Other fibres, sensory in function, run in
from the peripheral parts of the body and the gills.
A stimulus such as a difference in the constitution of
the water, a shadow thrown on the mantle edge, or a
blow struck by some external object on any soft part
of the body, is followed by the transmission of nerve
impulses to ganglion cells and from these to muscles.
A response may or may not follow the stimulus, but
we can only regard it as a reflex action.

40 PEARLS [CH.

The Reproductive System.

The last system in the body to which we shall
allude is the one comprising those organs upon
which the upkeep of the race depends. In the pearl
oyster the sexes are separate, that is to say, an
individual is either male or female. (In the scallop,
both male and female organs are found in each
individual. )

There is however no difference to the eye in the
external appearance of male and female oysters ; the
sex can only be determined by examining closely
the organs of reproduction inside the body. The
organs themselves are rather diffuse, and consist of
hundredsof branched tubules which cover the stomach,
the digestive gland, and the intestine. The tubules
open into little sacs, and in these the eggs or sper-
matozoa are formed, according to the sex. The
tubules join up to form ducts which open into each
other until they form a large duct on each side which
opens to the exterior. When the reproductive organs
are mature, the eggs or spermatozoa are shed into
the sea. They pass out of the shell and float about
in the water in which the animals are living. As the
spermatozoa are developed in countless numbers and
as the pearl oysters are gregarious, there is every
chance of a sperm meeting an egg. Fusion of the
two then takes place and fertilisation is accomplished.

a

m1] THE PEARL OYSTER 4]

Fertilisation depends then not upon any act of the
pearl oysters themselves, except of course the emis-
sion of the eggs or sperms into the sea-water, but
upon the accidental meeting in the sea of the two
microscopic germs.

Where this method is adopted we always expect
to find myriads of eggs developed in the individual,
to make sure in the terrific mortality that afterwards
occurs that some small but adequate proportion will .
survive. This is the case in the pearl oyster. It
would be a tax on the imagination to picture what
would happen if every egg produced by the pearl
oysters developed into even a young oyster. This,
however, applies to many thousands of other species
in the animal world.

The description of the pearl oyster should give an
idea of the type of animal that is popularly known as
a bivalve. It would not be difficult for the reader to
find most of the structures described in the edible
oyster, the scallop, the clam, the edible mussel, cockle
and fresh-water mussel. The three last-named might
look rather different, but this is simply due to the
fact that instead of possessing one large central
muscle for closing the shell, they possess two, one at
each end of the body.

42 PEARLS (cH.

CHAPTER IV

THE LIFE-HISTORY OF THE PEARL OYSTER, AND
THE CONDITIONS UNDER WHICH IT LIVES

THE mature pearl oysters, as we have seen, dis-
charge into the sea their sexual products, eggs or
- spermatozoa, according to the sex. The actual
emission has been observed in May for Ceylon
oysters, but probably the spawning season extends
over many months of the year.

The eggs and spermatozoa pass out direct from
the reproductive organs into the water, which is con-
tinually passing into and out of the pallial cavity.
Fertilisation of the eggs takes place in the sea-water.
There is however a very great probability, as the
author has observed in the case of other lamelli-
branchs, that the emission of ripe spermatozoa from
the male is stimulated by the presence of female
oysters.

As the pearl oyster is a gregarious animal like
our own edible mussel, there is every chance of the
numerous eggs being fertilised, even though no act
of copulation brings the sexual products together.
This method of fertilisation of the eggs may be taken
as holding good for the other relatives of the Ceylon
Pearl Oyster—the Mother-of-Pearl Oysters—and also

Iv] LIFE-HISTORY AND ENVIRONMENT 43

for our edible mussel. It does not hold good, how-
ever, for the fresh-water mussels of our streams and
lakes, the life-history of which will be discussed
further on. The small egg, at first irregular in
shape, but becoming spherical after fertilisation,
floats in the sea at the mercy of any current over
the banks; but development continues, and we soon
have a little multicellular embryo which swims by
means of cilia. This power of locomotion is of course
of no account in determining the wanderings of the
embryo, which, during its entire life, is dependent
upon the erratic currents in which it floats. The
second day marks the appearance of a tiny shell
which develops until a minute transparent bivalve
shell encloses the larval oyster. It is still a swimming
form living as a floating organism. This brings us
to the stage immediately before the formation of
“spat.” The term “spat” is given to the earliest
attached stage in the life-history of molluscs like
the pearl oyster. The attached stage is probably
reached just within a week after fertilisation has
taken place.

It will be seen that the chances are very great
that during this time the free swimming embryo has
been carried by tidal currents far away from the
home of its parent oysters. It may perhaps be taken
over a great oceanic abyss, or a sea-floor quite
unsuitable for its attachment, in which case the adult

44 PEARLS [CH.

stage would never be reached. It is often quite easy
to provide artificial supports to which the pear] oyster
and other shellfish spat can attach themselves when
natural objects are wanting. Thus, for example, at
places on the French coasts, attachment areas are
prepared for the edible oyster and mussel. Drain
pipes, placed in shallow water, have served as very
favourable objects for the young spat of the scallop.

The shell valves now continue to grow, increasing
in thickness, but retaining for some time their trans-
parency. The larval swimming organ becomes re-
‘duced and disappears, and the shell-closing muscles
and foot develop. These tiny oyster spat are only
about 0°l mm. in diameter.

If they have only sandy wastes as sea bottom it is
certain that their life is short. Hence there is im-
mense need for favourable grounds, with either hard
objects or with seaweeds to the fronds of which the
young spat can attach themselves.

The young pearl oyster is an actively moving
organism, even though it attaches itself by means of
a byssus. In this again it resembles many other
common bivalves. The method of locomotion can be
well seen if a quite small active edible mussel or a
very young scallop is placed in a glass vessel of sea-
water.

The animal attaches itself to the glass by means
of strands of byssus secreted in the way already

Iv] LIFE-HISTORY AND ENVIRONMENT 45

described. Holding on by these strands the animal
pulls itself nearer to the point of attachment, then
stretches out its foot and proceeds to secrete other
byssal threads and to attach them further away, on
the glass sides of the vessel. As soon as a firm hold
is obtained the old byssal threads are thrown off by
the animal and remain adhering to the glass. This
process is repeated time after time, and the track
followed by the mollusc is indicated by the series of
cast-off byssal threads.

Apparently the young pearl oysters do not travel
so fast as young scallops (which as a matter of fact
are famous throughout life for their powers of
locomotion). They are sensitive to light and, in
aquaria, move but little during the day. Probably
this does not apply at the bottom of the sea on the
pearl banks. During the first two years of life the
pearl oyster grows rather quickly. The age and
the size at which they are fishable, vary for the
different species. The Ceylon pearl oyster has to
battle with its enemies until it is four and a half
to five years old. It is then roughly about three
inches in height and two and a half inches in breadth.

The life-history of the fresh-water mussels in
rivers and lakes is very different. The mussels live
in clear water and on stony or sandy ground, either
isolated or in great numbers.

They do not emit eggs outside their shell, for

46 PEARLS [CH.

these and also the young larvae which might develop
would be swept down by the current into the sea.
The eggs are kept inside the parent and develop into
peculiar larvae with tiny shell valves provided with
hooks.

. These young mussels are set free and clap their
shells vigorously. If by a happy chance they strike
some fish swimming in the water, they attach them-
selves and actually live partially embedded in the
tissues of the fish forsome weeks. Atthe end of that
time they drop out as young mussels and take up
their normal life on the bottom.

It will be advisable now to look more closely at
the conditions under which some of these pearl-
producing molluscs live.

As it is beyond the scope of this little book to
discuss the homes of all the various pearl and nacre-
producing molluscs, it will be more satisfactory to
glance at the habitat of the Ceylon pearl oyster
as an example.

The animals are found mainly on certain banks,
which are part of a submerged plateau in the Gulf of
Manaar, off the north-west coast of Ceylon. These
banks are known as “ paars ”—a name which implies
a hard bottom of any kind. They are situated in
depths of from five to about ten fathoms.

The pearl oysters, like most of our molluscs,
require a particular kind of sea bottom. In addition

Iv] LIFE-HISTORY AND ENVIRONMENT 47

to suitable conditions of depth, temperature and
water, they must have some objects to which they
can firmly attach themselves. One does not find
pearl oysters, therefore, on the fine ooze which exists
further out from the island at greater depths. Again,
pearl oysters are not found on the hard bottoms from
twenty fathoms down to a hundred fathoms, although
in many of these places large encrusting organisms
like corals and sponges are found in great abundance.
The pearl-bank plateau off Ceylon is broken up into
a considerable number of paars, from three to eighteen
miles from land. The plateau is for the most part
composed of sand, but here and there the actual
bare rock appears, although in many places it is only
covered by a few inches of shifting sand. This sand
was examined by the author in connection with Pro-
fessor Herdman’s visit to the pearl banks. It con-
sists of, sometimes, 40—50 °/, of skeletons of certain
protozoa called Foraminifera, many of them attaining
the size of a threepenny-piece. The remainder is
made up of sand grains and calcareous animal remains.
The rock itself is only a “cemented sand,” for the
sand grains in this sea-water with the calcareous
animal and plant remains become cemented together.
Lumps of coral and encrusting animal skeletons play
their part, and we have in consequence a modern
rock formation before our eyes.

Many of the rocky blocks—composite structures

48 PEARLS [ CH.

of the inorganic and organic worlds—are veritable
“marine biological stations” in themselves. Formed
largely of the remains of corals, foraminifera, sponges,
calcareous algae and sand, they are burrowed into
and provide homes for tiny crabs and shy crustacea.
Worm tubes, in which live beautiful tube-worms,
wind about the surface. A patch of a colonial
polyzoan, allied to those incrustations often found
on seaweeds round our coasts, and perhaps a dozen
or so pearl oysters hanging on by the byssus may
complete the catalogue of some of the more con-
spicuous organisms.

That arch enemy of the mollusc all the world
over, the starfish, is certain to be found creeping
about amongst its fare, and sea urchins and sea
cucumbers (close relatives of the starfish and not
vegetables, as the name might imply) represent the
Echinodermata.

The well-known seaweed-covered rocky beds of
our own coasts are very different. The seaweeds in
these tropical waters are enclosed in lime and might
well be mistaken for non-living things. In many
cases the plants live enclosed in the bodies of the
animals! Indeed, in these tropical regions where
the nitrogenous compounds so essential to plant life
seem to be deficient, the vegetable cells have been
driven to live inside the animals. This phenomenon
—of plant animals—is represented of course in our

Iv] LIFE-HISTORY AND ENVIRONMENT 49

climes by the green hydra, and that interesting worm
so ably described by Prof. Keeble in one of the
volumes of this series.

The basis of a paar may be said to be those hard
bodies to which young and old oysters can attach
themselves. This is known as “culch,’ and consists
of dead corals, lumps of calcareous algae, and old
shells of various species. In many places there are
suitable banks where the area occupied by sand
alone would be available for pearl oyster occupation
if “culch ” were present.

Artificial culching, that is, the bringing of suitable
material, such as shells, coral blocks or rubble from
other places and depositing it on the sandy bottoms,
might easily increase the extent of the oyster beds.
Somewhat similar methods have been adopted on the
coasts of France and Holland, and various structures
have been built up for the attachment of young
edible oysters or mussels.

If we consider all the surroundings, solid and
liquid, living, dead and inorganic, as making up the
environment of the pearl oyster, we find there are
favourable and detrimental features. The favourable
conditions have been touched upon ; let us now look
at the factors which lead to destruction. One of the
most important agents in causing the death of the
pearl oysters is the shifting of sand.

This is occasioned by strong currents raised. by

D. 4

50 PEARLS [CH.

monsoons and storms. The oysters are buried—
young oysters are destroyed, and in some cases the
destruction is enormous. Herdman and Hornell ob-
served the loss of “thousands of millions” of young
oysters from this cause in a year. On some of the
paars this depletion seems to be of regular occurrence
every year.

Next we come to the natural enemies of the
mollusc, and they are numerous, though probably
only a few commit serious damage. The “ black-
listed” animals are in the first place the fishes which
devour oysters. They are chiefly skates and rays of
different species, and the file-fishes. The large rays,
up to a dozen or more feet across, have been observed
feeding upon the shellfish. With their broad-surfaced,
specially adapted crushing teeth they can make short
work of the delicate shells ; and shell fragments, the
result of their depredations, are often numerous. The
file-fishes feed upon immature oysters.

The next group of enemies is that of the molluscs
which bore into shells. The gastropoda (univalves
like the common whelk of the English coast) are
provided with a proboscis armed with a chitinous
file. In addition, however, to boring holes by this
means and then inserting the proboscis, it is quite
certain that many of these univalves either catch an
unsuspecting bivalve with its shell open, or drive part
of their shell between the valves of their prey and

Iv] LIFE-HISTORY AND ENVIRONMENT 51

then attack the muscle. If this happens, the empty
shells of the oyster alone are left, perhaps uninjured
and with nothing to indicate the mode of death.

Certain sponges (Clione) bore into the thickness
of the shell valves just as they do in the scallops of
our seas. The valves are honeycombed in all
directions until they become completely rotten.
More serious, however, than these animals are the
starfish. Herdman records the destruction of be-
tween 200 and 300 a day when the ss. Veolet, in
the fishery of 1905, was dredging for pearl oysters.
This must give a huge total for the starfish living
on the paars.

Starfishes have, too, such powers of regeneration
that, other conditions being favourable, they are
little disturbed by being torn into two. They are
very voracious, and have reduced the opening of
oysters to a fine art! In one case Herdman and
Hornell considered that the disappearance of 5? mil-
lion oysters in a year was probably due to this enemy.

So much for the environment. It must not be
forgotten, however, that to any one oyster the other
brother oysters are also parts of the environment.
If therefore the young oysters are overcrowded, a
large number will die through interference with
nutrition. The competition for food is a greater
factor in the history of this universe than perhaps
many of its inhabitants believe !

4—?

52 PEARLS [CH.

The difficulties under which the pear! oyster lives
have been briefly touched upon. Finally, man him-
self, by his heedless removal of millions of breeding
oysters, is not the least of the enemies of the pearl
oyster, and a failure of the pearl-fishery must often
be attributed to his influence.

CHAPTER V
PEARLS

THERE is no little difficulty in making out from
the literature and from “common knowledge” what
is actually meant by the term “pearl.” Some dic-
tionaries are most ambiguous on this point. For
example, in the same paragraph we are told that
a pearl is “a silvery white smooth and iridescent
gem, extracted from the pearl oyster”; “something
round and clear, like a dewdrop”; “anything very
precious.” No doubt the term pearl is applied to
many beautiful objects in poetry and literature, but
so far as we are concerned, the name will have to be
used in a more restricted sense.

A pearl consists of a number of layers of organic
and inorganic matter, arranged more or less regularly
round some common centre (termed the nucleus) and

OO ae

v] PEARLS 53

resembling in composition and microscopic structure
certain layers of the shell of the mollusc in which
the pearl has been formed. It may be of almost any
colour and may lack altogether the lustre and general
appearance that is commonly associated with pearls.
As a matter of fact pearls are nothing more than
abnormal products, calcareous pathological bodies
formed, owing to some irregularity, in the tissues of
certain shellfish.

Von Hessling gave the following as a definition of
pearls. “Pearls are shells converted into a spherical
form ; they possess the same histological, physical,
and chemical peculiarities, in so far as these do not
belong specially to the rounded shape, and both
undergo, in all the different stages of formation, the
same fate.”

As we have already, for this special purpose,
described the shell of a bivalve in the account of the
pearl oyster, it will be easy to apply this knowledge
to the structure of pearls.

It is necessary, however, before doing this to draw
attention to other calcareous bodies which are found
in molluscs, which may possess a pearly lustre, and
yet are not true pearls. These bodies are known
as blisters. They are very often formed owing to
foreign objects such as sand grains getting between
the shell and the mantle; they often arise in the
process of repair of shell perforations.

54 PEARLS [CH.

“Blisters” have a different mode of origin, there-
fore, and they are usually attached to the shell. They
may be very large, and are often cut away from
the shell and used in cheap jewellery. It is blister
formation that has been encouraged, as we shall see
in a later part of this chapter, by artificial processes
for trade purposes.

True pearls themselves are of two kinds,

(a) Cyst pearls (Herdman) or Parenchyma pearls
(Jameson),

(b) Muscle pearls (Herdman).

Of these, the former are the most important com-
mercially, and have formed the subject of most of the
scientific work on the origin of pearls. They are
usually spherical pearls which occur singly in the
mantle or in the soft tissues of the pearl oyster or
mussel. They may occur even some distance away
from the surface, embedded in the digestive gland or
so-called liver.

Muscle pearls were distinguished first by Herdman
(British Association Report, Southport Meeting, 1903).
They occur usually in large numbers in the muscular
tissue, Where the muscles are attached to the shell.
Fig. 5 indicates the positions where these pearls are
found in the pearl oyster of Ceylon.

Now, putting the definition of von Hessling in
another form, it may be said that pearls are bodies
consisting of layers of calcareous material with an

v] PEARLS 55

organic basis. The layers are arranged in a more or
less concentric manner, round a central nucleus, and
the four types of structure met with in the shell may
occur in the pearls.

Fig. 5. Diagram showing the positions most frequently occupied by
muscle pearls in the Ceylon Pearl Oyster. (After Herdman.)

These layers, it will be remembered, are the
periostracum (the most external, almost entirely
organic layer), the prismatic layer, the nacreous layer
(or mother-of-pearl substance), and the hypostracum
(the layer found where the large closing muscles are

56 PEARLS [cH.

attached to the shell). Some pearls consist entirely
of concentric laminae of a substance like the peri-
ostracum. These pearls are not common but are
sometimes to be found near the very edge of the
mantle. Naturally, they are somewhat brown in
colour and lack entirely the characters which are
associated with pearls in the popular mind.

Pearls consisting entirely of hypostracum-like
substance are to be found, often in large numbers, in
the muscles. In fact, many if not most of the muscle
pearls are composed of hypostracum.

Now, where the muscle pearls are abundant, large
numbers of calcareous concretions or calcospherules
are scattered in the tissues. Herdman and Hornell
suggested that the muscle pearls were formed around
these microscopic calcospherules. It is extremely
probable, as suggested by Jameson, that these calco-
spherules are in reality small pearls—probably of
a hypostracum-like substance. Round them may
be deposited more layers of hypostracum or nacre.
There is no evidence in any case to support the
view of Mr Southwell that the calcospherules are
calcareous depositions from the blood.

The pearls composed of hypostracum may possess
either an empty central cavity, a cavity containing
granules, or a small central nucleus of yellow peri-
ostracal-like substance. The calcium carbonate is
laid down round the centre in a manner strikingly

v] PEARLS : 57

like the hypostracal layer of the shell. Radiating
striae pass outwards, and in addition a delicate
concentric lamination can be observed.

Fig. 6. Section of a pearl composed of prismatic substance with
nucleus of periostracum-like substance. (From Rubbel.)

Pearls of larger size, consisting almost entirely of
prismatic-like shell substance are more common, but
it must be remembered that usually the periostracal

58 PEARLS | OH:
substance occurs too, both in the very centre as a
nucleus, and also in concentric layers alternating
with the prismatic substance (fig. 6).

The prismatic substance resembles closely that
same layer in the shell, in the manner in which it is
deposited, but the columns or prisms are radially
arranged in the pearl so that they are at right-angles
to the concentric laminae.

Most pearls consist of a nucleus, to which reference
will be made later, and more than one, perhaps all,
of the different varieties of shell substance. The
most important of these is of course the nacre.

The figure below is that of a nacreous pearl com-
posed of two pearls which have fused together. The
nuclei consist’ of periostracal substance and also
hypostracal substance. Round these nuclei there
are concentric laminae of nacre with two rings of
periostracum. These concentric layers of peri-
ostracum may spoil the appearance of a pearl, com-
posed otherwise almost entirely of nacre. In the
same way, layers of prismatic substance may interfere
with the continuous deposition of the nacre.

Owing to the deposition of the layers in con-
centric form, it is possible for a clever jeweller to
strip off the laminae, just as the “skins” can be
removed from an onion, though of course the laminae
of nacre are never continuous right round a pearl.

This process of skinning the pearl consists in

v] PEARLS 59

removing the outer layers, if they are bad. There is
a great element of chance in the process, because one
never knows whether the deeper layers will be better
or worse, and each layer removed reduces the size
and value of the pearl.

Fig. 7. Section of nacreous pearl, really composed of two fused
pearls. Note the nuclei of Hypostracum and the concentric
dark layers of Periostracum. (From Rubbel.)

In any case the external appearance of a pearl
gives no clue to its internal structure, and the reason
for this follows from the description of the structure
given above.

There is some little difference between the nuclei
of pearls. Thus the pearls from the common edible

60 PEARLS [ CH.

mussel (Mytilus) have often very large nuclei. The
pearls from the Ceylon pearl oyster on the other
hand have small nuclei. The nucleus is an extremely
important body because of the part played by it in
the origin of pearls.

It is, moreover, around the question of the nucleus
that the various theories of pearl formation have
been built up.

The nucleus, in fact, is supposed by its presence
to have stimulated the shellfish, so that it secreted
the various layers of shell-like substance around it
and thus formed a pearl; or, more correctly, to have
caused the formation of a little sac of cells which
poured out these same substances. The nucleus
may be a foreign body or it may actually be one of
the substances found in the shell layers. We have
seen for example that in many pearls the nucleus is
a substance like the periostracum or the hypostracum
of the shell.

In other cases, however, the nucleus is a micro-
scopic animal parasite, a young larval worm which
has penetrated into the body of the shellfish and died
because of its encasement in a tomb of pearl. Sand
grains and other hard fragments from the external
world may also be found as the nuclei of pearls.

The composition of pearls must vary according to
whether they consist of periostracum or of the other
more calcareous layers. Leaving out of the question

v] PEARLS 61

the pearls of periostracum and taking pearls pos-
sessing an outer covering of nacre, we have the
following analyses :

Harley.
Calcium carbonate a 0 aia
Organic matter... ee 5°94
Water ee ie as ae
Loss - rae pe O11
Dubois.
Calcium carbonate ee 91°59 °/,
Organic matter... Te 3°83
Water iy ie Se 3°97
Residue __... fee 0°81

An analysis of nacre from the Ceylon pearl oyster
shells gave the following (Roaf) :

Calcium carbonate ‘H 88°79 °/,
Calcium sulphate ... are 4°93
Organic matter... Hae 2°32
Water is ot be 2°28
Loss ... ue a. fe 1°68

The calcium carbonate occurs in the form known
as aragonite.

So far as hardness is concerned it may be said
that some pearls require a hammer to break them.
This property varies greatly with the structure of
the pearl.

Moebius found that pearls were scratched by

62 PEARLS [CH.

apatite: in Mohr’s scale, this occupies the position
indicated in the following :
Apatite 5, Orthoclase 6, Quartz 7,
Topaz 8, Diamond 10,

and the pearl is therefore easily scratched by many
other stones. The specific gravity of oriental pearls
varies, but the average may be taken as being from
2°650 to 2°686. The specific gravity of fresh-water
pearls seems to be higher,.7.e. 2°724. Poor pearls
are not nearly so heavy and the specific gravity may
be much less—averaging 1°5 in fact.

In addition to the smaller spherical true pearls,
there occur irregularly rounded bodies, often of very
considerable size, known as baroque or baroche
pearls. These are sometimes mounted in jewellery
so as to hide their irregularity, but many have been
used so that their very irregularity added to their
value. At the beginning of the 18th century’ there
was quite a popular craze for baroche figures.
Curious, quaint men and animal figures were con-
structed with the aid of the pearls and precious
metals. Many of these are to be seen in the British
Museum. There are good collections, too, in the
Louvre and in the Dresden Museum.

At the present time small baroche pearls are
being mounted in necklets and bracelets.

The colour of pearls varies very considerably, and
all the possible shades between pure white and black

a TT LL

v| PEARLS 63

are known to exist. White, or as nearly white as is
possible, is usually regarded as the most sought after
and perfect tint. Colour alone, however, is not nearly
sufficient and there must be in addition a peculiar
kind of lustre.

It is this combination of tint and lustre that has
made the Ceylon pearl of such great fame and value,
and although equally good specimens often occur in
other places, even in fresh-water molluscs, on the
average the Ceylon pearls seem to be better than
those from most other localities. Many of the colour
effects are not due to the presence of actual pig-
ment but rather to reflection and refraction pheno-
mena. Thus one may have white pearls with a blue,
a green, or a pink sheen, although yellow is by far
the most common. Other pearls with more definite
colours and darker tints generally possess little or
no lustre, and some of these would hardly be con-
sidered true pearls at all by dealers.

This often applies to the pearls found in the
common edible mussel. In fact, supporting this
remark, we find in the glossary of one book on pearls
a definition of true pearls as follows: “ Pearls formed
of nacre as distinguished from similar formations
which are not nacreous.’ It is not at all necessary
for a true pearl to have any of the nacreous layer
represented in its structure.

The black pearl does not seem necessarily to be

64 PEARLS (OH.

black! A really black pearl is a gem of some value,
but most so-called black pearls are merely deep
shades of brown, or dirty blue. Nearly all the
varieties of colour are to be found amongst fresh-
water pearls. This agrees with the statement made
long ago by the Venerable Bede to the effect that
the British pearls were “ of all the best colours—that
is, both red and purple, jacynth and green, but
principally white.” It is: quite easy to see that a
series of selected pearls in a necklace will be of
greater value than individual pearls of the same size.
It is said in fact that if you match a pearl with
another, you double the value of each of them. The
reason of course is the difficulty experienced in
finding amidst specimens which vary so much in tint,
lustre and shape, two that will stand the test of being
viewed together. For definitions of some of the
many names applied to pearls, reference should be
made to the glossary at the end of the book.

It is not surprising, in the present day of imitation,
that we should find remarkably good artificial pearls.
By artificial pearls I mean actually manufactured
articles, and not those structures which are secreted
by the molluscs after stimulation by man. That is
artificial stimulation, and the “pearls” produced are
eally on ly “blisters.” Very many of these imitation
pearls come from France, where, as a matter of fact,
the industry was created.

vy] PEARLS 65

Globules of glass are used in one method. These
are made of an opal-like tint and then treated with
a special mixture known as “essence d’orient.” It
“consists of the iridescent guanin from the scales of
a fish—whitebait.” The scales are removed from
the fish, and rubbed in fresh water until they lose
the iridescent substance. This is abstracted from the
water and kept in ammonia. A drop of the essence
+s introduced into the inside of the bead of glass and
the internal surface of the latter coated uniformly
with the mixture. The bead is then filled with wax.
Other variations of this method are used.

Imitation pearls are sometimes made by cutting
out spherical pieces from mother-of-pearl shell and
polishing them.

Even artificial mother-of-pearl can be made now
in pieces of considerable size. Substances allied to
celluloid are prepared which are treated with “essence
dorient.” Naturally the structure of these imitations
whatever be their appearance is quite different from
real mother-of-pearl.

The trade in these purely artificial products is
of considerable value and imitation pearl necklaces
are to be seen in shops in some of the best London
streets.

We cannot close this chapter without referring in
conclusion to the attempts that have been made to
stimulate shellfish to produce true pearls. This is

D. 5

66 PEARLS [cH.

one of the lines along which biological science has
at various times exerted its influence. As a matter
of fact, the artificial production of pearls has so far
proved a greater commercial success than the culti-
vation of the pearl oysters. Great care must be
taken, however, to distinguish between true pearls
and blisters, and most, if not all, of the artificially
stimulated pearls are really only blisters, and so of
comparatively little value.-.

The natives of the far East recognised many years
ago that if a foreign body was insinuated between
the shell and the mantle of nacre-producing mol-
luscs, the irritating object would be covered with
a layer of nacre. Sometimes small worms or even
fish get into this strange position, and become
coated with nacre (fig. 8). A beautiful specimen of
this is to be seen in the British Museum. Hague
describes how the Chinese carried on a manu-
facture of pearls in this way in the fresh-water bivalve
Dipsas plicatus. The shellfish were collected and
kept living in lakes for this purpose. They were
first opened (usually by children) and then objects
of various kinds (grains of sand, pellets of nacre, or
images of Buddha) were inserted between shell and
mantle. After about ten months or longer, up to
three years, the shellfish were fished up and the
nacre-covered objects removed and sold.

The nacre-covered pellets were naturally the most

v] PEARLS 67

like true pearls. This industry of the Chinese has
been of considerable value and of some import-
ance in the districts where it was carried on. The
practice has, moreover, been rather general in the
East and it is applied now on a larger scale by the
Japanese. There is no reason why the method should
not be successful in any mollusc, the shell of which
possesses a pearly nacreous layer. The pearls pro-
duced are only blisters and attached to the shell,
but in these days of cheap jewellery, a little care in
mounting hides the weak spots and blemishes.

The great Swedish naturalist Linnaeus turned his
attention to the production of pearls by artificially
stimulating shellfish, and with a reference to his
work we shall conclude this chapter.

In various works on pearl formation, references
occur to the “secret process” of Linnaeus, but what
this may have been was not known until quite re-
cently. That Linnaeus did produce pearls seemed
certain, and most writers on pearls simply made
guesses as to the modus operandi. Herdman’s
curiosity was aroused by the numerous references,
and by a search through the manuscripts in the
Collection of the Linnean Society, London, he ar-
rived at the truth. The letters and other documents
are extremely interesting and begin with a letter
to Colonel Baron Funck (dated Feb. 1761), in which
Linnaeus states “that he ‘possessed the Art’ of

5—2

68 PEARLS [CH.

impregnating mussels, and that he offered to make
known the secret for the public benefit and use on
condition that the state would give him a suitable
reward'.” The secret method seems to have been
the following :

Ist. A small hole was made in the mollusc shell ;

2nd. A fine silver wire was inserted bearing at its
end a small rough fragment of limestone;

3rd. The artificial nucleus had to be kept near
the ends of the shell so as not to irritate too much
the animal’s body;

4th. The nucleus was kept away from the shell by
means of the silver wire, otherwise the pearls would
have been connected to the shell by nacre deposits.

The mollusc used in the experiments of Linnaeus
was the fresh-water mussel.

CHAPTER VI
A CEYLON PEARL FISHERY.

AN account of a Ceylon pearl fishery will best
serve as an example of the oriental industry. The
pearl fishery of this part of the world is probably
of very great antiquity, and it was very likely carried

1 Herdman, Presidential Address to the Linnean Soc., May 1905
(see Proc. L. S.).

VI] A CEYLON PEARL FISHERY 69

on 2000 years ago in much the same simple way as
at present. We have already seen how the Singhalese
records go back hundreds of years before the Christian
era. Let us now look at one of the recent fisheries.
The Ceylon fishery is and always has been an inter-
mittent one. At the present date it does not exist
at all. Records show that throughout the centuries
there has been the same sequence of productive
years and bad years. More recently the hand of
science has been called upon to alter the stern
decrees of nature, but the call seems to have come
too late to stave off the present cessation of the
industry. In the 19th century there were only
36 fisheries. Sometimes, after a few good years
there would be a long spell without any fishery.

How long the present unproductive period will
last. none can tell. Neither can one say yet what
combination of circumstances will cause the re-
plenishment of the submerged banks with pearl
oysters, although we may guess at the causes of
depletion.

Herdman’s visit to Ceylon in 1902 was after
twelve years of unproductiveness, and it was just at
a time when the banks were beginning to show signs
of another fishery. The promise was fulfilled and
for some years there was a truly remarkable series
of fisheries—fisheries of very great value to the
controllers. In fact, as more than one writer has

70 PEARLS (CH.

said, the pearl fishery is the greatest gamble of the
world. From the very commencement to the end
the procedure is guarded and cared for by “fickle
fortune,” and it requires very little knowledge of the
East to appreciate the excited condition of the
natives of Ceylon and even India and more remote
parts during a fishery. In olden times it was rumour
which collected the divers. They heard from afar
that the harvest was ripe and they came to the
banks with zest to take part in the lottery. For
some hundred years, however, the Gulf of Manaar
banks have been carefully examined every year by
a Government inspector, and the Ceylon Govern-
ment has decided whether there would be a fishery
or not. The fishery takes place in February, March
or April, while the inspection was usually in
November.

The fact that a fishery is to be held is now made
known by the newspapers, but probably passes just
as quickly in the more ancient way from mouth to
mouth until the whole of the Orient is informed of
the fact. The advertisements in the newspapers are
printed in Cingalese, Tamil and English. A notice
of the fishery of 1905 is appended.

VI] A CEYLON PEARL FISHERY 71

“Ceylon Pearl Fishery of 1905.

“Notice is hereby given that a Pearl Fishery
will take place at Marichchikkaddi in the Island of
Ceylon, on or about February 20, 1905.

“The Banks to be fished are the South-West
Cheval Paar, which is estimated to contain 3,500,000
oysters, sufficient to employ 200 boats for two days
with average loads of 10,000 each a day ; the Mid-East
Cheval Paar, estimated to contain 13,750,000 oysters,
sufficient to employ 200 boats seven days with average
loads of 10,000 each a day. The North and South
Moderagam, with 25,700,000 oysters, sufficient to
employ 200 boats for thirteen days with average
loads of 10,000 each day; the South Cheval Paar,
estimated to contain 40,220,000 oysters, sufficient to
employ 200 boats for twenty days with average loads
of 10,000 each a day; each boat being fully manned
by divers.

“2. It is notified that fishing will begin on the
first favourable day after February 19. Boat
owners and divers should be at Marichchikkaddi by
February 16. |

“3. Marichchikkaddi is on the mainland, eight
miles by sea south of Sillavaturai, and supplies
of ‘good water and provisions canbe obtained
there.

“4, The fishery will be conducted on account of

72 PEARLS [cH.

Government, and the oysters put up to sale in such
lots as may be deemed expedient.

“5, The arrangements of the fishery will be the
same as have been usual on similar occasions.
Persons attending the Fishery Camp from India will
be permitted to travel to Ceylon by either of the
following routes: (1) Tuticorin to Colombo or (2)
Paumben to Marichchikkaddi—and by no other.
Arrangements will be made as at the last fishery for
travellers to proceed from Paumben direct to the
Camp. The only restriction imposed on travellers by
the Paumben route will be inspection by the Medical
Officer at Paumben.

“6. Drafts on the Banks in Colombo or bills on
the Agents of the Government in India, at ten days’
sight, will be taken, on letters of credit being pro-
duced to warrant the drawing of such drafts or bills.
“7, For the convenience of purchasers, the
Treasurer at Colombo and the different Government
Agents of Provinces will be authorised to receive
cash deposits from parties intending to become pur-
chasers, and receipts of these officers will be taken
in payment of any sums due on account of the
fishery.

“8. No deposit will be received for a less sum
than Rs. 250.

“9, All communications regarding the fishery
must be addressed to the Government Agent,

vI] A CEYLON PEARL FISHERY 73

Northern Province, Jaffna, Ceylon, up to the end of
January, after which date they should be addressed
to him at Marichchikkaddi.

“By His Excellency’s Command,
“A, M. ASHMORE,
“Colonial Secretary.

‘*Colonial Secretary’s Office,
‘¢Colombo, December 16, 1904.”’

This fishery of 1905 was of very considerable
value. The temporary town of Marichchikkaddi was
larger than ever known before. The inhabitants
crowded in to it and were at least 10,000 more than
in the previous record fishery of 1904. The numbers
of oysters fished and the money obtained for the
Government of Ceylon were far beyond all previous
records. In fact, 81,580,716 oysters were taken and
the revenue alone was £167,381. In the three years
1903, 04 and ’05 the revenue amounted to £293,735,
quite enough to show the importance of this fishery
to Ceylon.

Now we may proceed to describe, first the events
of inspection which lead to a fishery, and secondly
the fishery itself.

There are numerous preparations necessary before
sailing for the pearl banks. Boats have to be re-
paired and painted, old stores overhauled and new

74 PEARLS [cH.

ones procured, and at the same time supervision
given to a steamer which may serve as an oyster-
dredger. The place selected as the centre of the
pearl fishery in 1905 was, as stated above, Marich-
chikkaddi, near the mouth of the Modragam River.
It is necessary to make an inspection of the beds of
oysters which it is proposed to fish immediately
before a fishery opens, so that the inspector, or
commander-in-chief of the fisheries, as we may term
him, may be in a position to mark off the ground
and regulate the number of boats and days allotted
to particular areas. The essential features of the
preparations are as follows: Three flag-buoys are
laid out by attendant launches in the direction of
each cardinal point of the compass, at distances
apart of 4-mile, the inmost buoys taking their dis-
tance from the inspection vessel, which is anchored
to serve as a pivot mark in the centre of the circular
area to be inspected. Then four boats (usually
modified whale-boats), each manned by a crew of six,
together with three divers and two munducks, under
the charge of an experienced coxswain, take up equi-
distant positions between the ship and the first flag-
buoy and row slowly round the ship, retaining with
wonderful accuracy their relative positions.

At regular intervals the crew rest on their oars
to allow the divers to make descents and bring up
oysters if any are present. The result of each dive

VI] A CEYLON PEARL FISHERY 79

is reported to the coxswain of the boat, who records
the condition of bottom and oysters upon a diagram
form with which he is provided. The oysters are
retained in the boat for the inspector to examine.
The four boats, having each made a complete circuit,
are next ranged in line abreast in the same manner
as before, between the }-mile and the 4-mile buoys,
and each then makes a second circuit. Lastly, there
is a third series of circles, so that the four boats
thus make a total of twelve concentric circuits, each
boat making three. The results shown upon the
four coxswains’ diagrams are transferred by the
inspector to a final diagram or plan furnished
with twelve concentric circles. When this is done
the inspector possesses a graphic diagram of the
average distribution of old and young oysters, and
the places where no oysters occur at all. He cal-
culates in square yards the area occupied by oysters,
and then the approximate number of oysters thereon
may be estimated by taking the average number
of oysters per dive (ascertained by examining the
divers’ results), in conjunction with the average
amount of ground which a diver is credited with
being able to clear at one descent. Usually this area
is considered to be about three square yards, and by
assuming this to be a maximum area the danger of
overestimating the number of oysters is avoided.
Inspection estimates are usually less than the

76 PEARLS | [cH.

total number of oysters obtained at the ensuing
fishery.

The actual number of oysters is, however, not the
main object of the fishery, the important question
being the determination of the probable value of the
pearls which will be obtained. It is necessary, there-
fore, for an official valuation to be made of the gems
obtained at the inspection for the purpose of ad-
vertising the fishery. Consequently, during intervals,
three large samples of oysters of fishable age are
obtained, partly by means of divers and partly by
dredging. The weight and the number of the pearls
to each 1000 oysters are calculated, the particular
place from which the oysters are taken being
noted.

The next procedure is to mark out the fishing
ground, and to make known the meaning of the
marks. The method is rather a novel one. The
boundaries of the fishing ground are marked by
buoys bearing red flags, while a series of white-
flag buoys are placed wherever fishable oysters are
present. The divers are instructed to cluster their
boats round the various white flags. The oyster
buoys are placed according to the distribution of
- oysters mapped out after the inspection, but to guard
against the possibility of mistake the abundance of
oysters may be verified by preliminary dives before
anchoring the buoys in position. The flag system

VI] A CEYLON PEARL FISHERY 77

may be further improved by marking the flags in-
dividually with distinctive numbers and signs.
Advertisements are then published throughout the
Kast, especially in the vernacular, in papers reaching
the Persian Gulf and the two coasts of Southern
India, at the instance of the Colonial Secretary’s
office at Colombo. As a result of these advertise-
ments divers, gem-buyers, speculators, moneylenders,
petty merchants and persons of very diverse occupa-
tions, make speedy arrangements for attending the
fishery. Indian and Cingalese coolies flock by the
thousand to the coast, longing to play even humble
réles in the great game of chance. The “ tindals”
and divers provide boats and all essential gear for
the work afloat, while ashore the Government supplies
buildings and various forms of labour. Stories of
the mushroom growth of towns wherever gold is
found, or diamonds discovered, or oil struck, have
become quite commonplace. Tales of the uprising
of Klondike, Coolgardie, and South African cities
fade beside Marichchikkaddi—the city with no
foundation. Among its thousands of inhabitants
are only a few hundred women who merit the right
of being present through serving as water-carriers
to camp and fishing fleet. This place, with its un-
pronounceable name, is the pearl metropolis of the
universe. Probably there is not a stocked jewel
case that does not contain gems that have filtered

78 PEARLS [CH.

through this unique city by the sea. It is a place
that comes and goes like the tide’s ebbing and flow-
ing. A sand-drifted waste lying between the jungle
of the hinterland and the ocean is transformed by
the “open Sesame” of a fishery proclamation into
a seething mass of working humanity in a few
weeks. Sheltering roofs are erected, and a struggle
for gain is prosecuted with an earnestness that would
have borne golden fruit: in any city in the Western
World. Public buildings, almost pretentious in size
and design, rise from the earth in a few days—a
residence for the Governor of Ceylon; one for the
Government agent of the province; and another for
the delegate of the Colonial Office. Amongst other
buildings are to be found a court-house, treasury,
hospital, prison, telegraph-office and post-office and
a fair example of that blessing of the East, known
as a rest-house.

Sites on the principal streets are leased for the
period of the fishery, and for ten or twelve weeks
Marichchikkaddi is one of Asia’s busiest marts. One
would hardly think that these Easterners, squatting
on mats in open-front stalls, could judge the merits
of a pearl, yet they can estimate the worth of a gem
with a wonderful precision. Usually they have learned
by long experience every “point” that a pearl can
possess, knows whether it be precisely spherical,
and has a good “skin” and a lustre appealing to

vi] A CEYLON PEARL FISHERY 79

connoisseurs. A metal colander or simple scale
enables them to know to the fraction of a grain the
weight of a pearl, and experience and the trader’s
instinct tell them everything further that may pos-
sibly be known of a gem.

When fishing is at its height, the scene on the
banks is one of extreme animation. Each craft is a
floating hive of competitive noise and activity. Ali
around are disappearing and reappearing seal-like
heads. By noon most of the divers are tired out
and, if it has been a successful day, the boats are
fairly loaded up. A gun is fired from the Master
Attendant’s ship, and this gives the signal for pulling
up the anchors, hoisting the sails and beginning the
run home. The men, other than the tired-out divers,
occupy themselves nominally in picking over their
oysters, throwing away stones, shells, and other
useless things, and in preparing the loads for easy
transport from the boats to the shore. But, as a
matter of fact, it is well known that this opportunity
is seized to “pick” the oysters in another sense.
Almost invariably the finest pearls occur just inside
the edge of the shells, and may fall out at any
moment. No doubt many of these round and best
coloured pearls are picked out during the run home
and concealed about the persons of the boats’ crew.
This is one reason why the Government does not get
its fair share of the pearls.

80 PEARLS | [cH.

The homeward race of a hundred or so ruddy-
sailed craft before a strong wind and over a tropical
sea is a very pretty sight. They are orientally
fantastic in colour and shape, and each deck is
crowded with men and boys, with shining brown
skins and brightly coloured cloths wrapped round
them. Each crew strives to get in first, because—
“first come is first served,” and they who first dispose
of their loads are the first to be free to rest. The
load is counted and divided into three piles. An
official selects two piles for the Government, whilst
the other is divided among the divers. On their
way to their houses these divers are besieged by a
surging crowd of natives eager to buy from them
their oysters by the dozen or by the half-dozen, or
even singly. They may be observed stopping at
boutiques and paying their score with oysters, ex-
tremely acceptable to the shopkeeper itching to try
his luck. In a small way oysters pass current here
as the equivalent of coin.

In the meantime those oysters belonging to the
Government have all been counted and at sunset
a great auction begins, the Government agent being
seated at a platform looking after the proceedings.
He announces how many of the oysters are for sale
and puts these up by the thousand. Any number
of thousand, from one to fifty or even more, are
taken by individual purchasers or by syndicates.

VI A CEYLON PEARL FISHERY 81

The competition to fix the price of the first lot takes
about a minute. The prices in a single night vary
considerably and inexplicably; a high price, say
35 rupees per 1000, may be given at the beginning
of the evening, and later not more than 22 rupees
can be extracted. There is a keen and zealous com-
petition, the larger buyers competing against the
smaller, or all combining in a ring against the Govern-
ment auctioneer. The day’s catch is generally sold
within the same night, but if not, the balance is dis-
posed of privately the next morning.

Early the next day each purchaser comes to the
Government agent with an order for the number of
oysters knocked down to him the previous night, and
sets to work to remove them to his own shed.

The washing of the pearls from the oysters is a
most tedious, primitive, and somewhat disgusting
process. The oysters are simply left to rot, the
process being much assisted by vast numbers of a
species of blow-fly, which after the first day or two
infests the whole camp. The maggots of this fly
eat their way through everything. After a week’s
rotting, the seething and disgusting mass is sorted
by hand and the pearls, or such of them as are of
sufficient size, are picked out. The residue is now
ready to be washed. This is carried on in dug-out
canoes or “ballams.” The bivalves are put in and
water is poured over them. As the water rises, a

D. 6

82 PEARLS (cH.

wriggling mass of maggots floats up from the lower
recesses. The shells are rinsed, and the valves
separated and rubbed to remove any detritus in
which a pearl might lodge. The men _ scrutinize
the nacreous lining for attached or shell pearls ;
placing any found in a special basket. After the
quantity has been reduced somewhat the floating
maggots are skimmed off. Some of the water is
baled out through a sieve, any material that remains
therein being carefully returned to the ballam lest
a pearl may be contained or entangled in the dirt.
More water is then added and the process of washing
the shells is continued. Finally, after all the shells
have been removed a fresh supply of water is poured
into the ballam until it overflows. By this method
the lighter filth is got rid of. The remainder
of the water is decanted and the heavy débris in
which the pearls are mingled is exposed at the
bottom. More water is added and the detritus or
“sarraku” kneaded and turned, over and over again.
This “sarraku” is sorted and winnowed at leisure,
and examined till the smallest sized pearls have been
extracted. The final search is carried on by women,
and it is amazing to see what a large quantity of
small pearls their keen eyes and fine touch enable
them to obtain.

After the pearls are picked out, it is customary
to offer the apparently exhausted dirt for sale, and

vi] A CEYLON PEARL FISHERY 83

ready buyers can always be found. In this manner
the pearls of our dainty necklaces and engagement
rings are wrested from Nature. The whole process
is-intensely interesting and picturesque, but it leaves
much to think about afterwards and much to hope
for. The thing has been going on in the same way
for centuries, and it would continue for centuries
to come if the busy Western mind, so full of new
ideas and plans, were not turning its attention to
improving the old system. What is wanted is to
make this harvest of the sea more regular in its
occurrence, to economise the vast expenditure of
human energy now wasted in bringing up the oyster
from the depths of the sea. The pearls might be
extracted from the oysters with greater rapidity
and certainty. More hygienic methods should be
employed and there should be more assurance that
the Government of Ceylon obtains its fair share of
the revenue.

CHAPTER VII
PEARL FISHERIES OF OTHER LANDS

The Persian Gulf. The fisheries of the Persian
Gulf, like those of Ceylon, have been exploited for
very many years. They were known in the time of

6—2

84 PEARLS [ CH.

Alexander and referred to by Pliny. By some, these
fisheries are supposed to be the most valuable in
the world and Seurat states that their revenue is
estimated to be 10 million frances annually.

The pearl oysters that are fished are the species
Margaritifera vulgaris (the Ceylon Pearl Oyster)
and a variety of Margaritifera margaritifera (per-
sica). The latter is shipped as Bombay shell. The
pearl oysters occur all along the coast of Arabia, but
the banks (like the paars of Ceylon) where the
fishing takes place, are situated near the island of
Bakrein. The centre of the industry is perhaps
Lingah, and the pearls are sometimes known as
Lingah pearls, though the term “ Bombay pearls” is
quite as frequently given to them. The former ap-
pellation refers to the place of origin and the latter
to the seaport from which they are shipped. Several
thousand boats are employed in the fishery but they
are usually smaller than the Ceylon boats and the
crew averages less than a dozen. ‘The method of
fishing is exactly the same as that practised by the
Arab divers at Ceylon.

The diver uses the same small basket of cocoanut
fibre, to which one line is attached, for the oysters.

There is also a line with a heavy stone at the end
of it. The diver sinks rapidly by entering the water
in a vertical position with one foot in the loop of the
rope at its point of attachment to the stone.

vu] PEARL FISHERIES OF OTHER LANDS 85

At the bottom, he gathers as many pearl oysters
as possible, places them in the basket, and when
ready gives the signal to be hauled up. The basket
alone may be hauled up with the diver hanging on
to it or there may be a rope round the man’s waist.

The fishery lasts from June to September when
the sea is at its best for this purpose. The pearls
from the Gulf are not so white or as fine as those
from Ceylon. Frequently they possess a yellow
colour. Curiously enough, however, in Bombay
these pearls seem to be preferred to the white.

The Red Sea Pearl Fishery is another ancient
industry. It was flourishing in fact in the time
of the Ptolemies. Two species of pearl oyster are
fished, a variety of WM. margaritifera, which is the
Egyptian shell of the trade, and also the Ceylon
species which is smaller in size and fished for pearls
alone. Jiddah was at one time the chief seat of the
industry, but now it has lost that position. The
pearls are finally exported from Alexandria and are
known as “ Egyptians.”

The Australian Pearl Fisheries are of very con-
siderable importance and are probably the largest
and best equipped at the present time in the world.

The fishing, for either mother-of-pearl shell or
for pearls, is carried on at various places on the
north-west, the north and north-eastern coasts.

For a quarter of a century pearl oyster fishing

Fig. 8. Nemertine worm and sand grains entombed in a
deposit of nacre.

vir] PEARL FISHERIES OF OTHER LANDS 87

has ranked as one of the primary industries of
Western Australia, being practised first at Shark’s
Bay. It has been pushed further north, and it is
stated that the naked diving and the beach-combing
of the aborigines financed many a settler in the early
years of his pastoral enterprise.

The Queensland fisheries are carried on along
the tropical coasts of that state and in particular in
the Torres Strait, where some attempts at pearl
oyster cultivation have been made. The Gulf of
Carpentaria is another home of the industry. The
custom of naked diving appears to be gradually dying
or to have already disappeared in Australia, and the
diving dress is usually employed. At the same time
the divers are largely Malays, Japanese, and Manila-
men, although the industry is financed by the Whites.
As it has been always believed that it was quite
impossible to have any but coloured labour, the
industry has enjoyed comparative immunity from
the rigorous “white Australia” laws of the Common-
wealth. It was decided, however, in 1911 that this
industry should conform to the laws of the country
and two years’ notice was given, so that this year,
1913, should see the employment of Europeans as
divers. From Western Australia alone, 29,281 cewts.
of pearl shell were exported in 1910, the value being
£246,068. The value of the pearls discovered brought
this sum up to £348,911.

88 PEARLS [cH.

The working expenses of a boat are about £500
per annum and pearl shell must be worth at least
£140 a ton to bring in any reasonable profit.

The pearl fishing of Japan is another extensive
one, and if we include China and Siberia we find
that as many as 20,000 men were actually em-
ployed in fishing in 1906. Japan is the first country
in the world to set up a pearl-farming industry
based upon scientific knowledge. The shell fished
in Japanese waters is Margaritifera martensii and
it is particularly abundant in the bay of Agu in the
province of, Shima.

The district where the cultivation is carried on
is also in this bay, and it is reported that as much
as 22 sq. nautical miles were leased in 1911.

American fisheries. Pearl fishing is carried on
on both sides of the continent of America. The
Panama coast is perhaps most famous, and it is said
that these pearl banks were discovered in 1530 by
Vasco Nunez of Bilbao. When Spain was an all-
important power in this part of the world, the
country was known as Colombia and large quantities
of pearls were sent to Europe.

The ancient fisheries of the Aztec kings were
carried on between Acapulco and the Gulf of Tehuan-
tepec. There are at the present time quite extensive
Mexican fisheries, the shell equalling in value the
pearls. The fishing seems to be systematic and new

vil] PEARL FISHERIES OF OTHER LANDS 89

beds are constantly being discovered. Both the
methods of naked diving and diving with dress
are employed. Another very extensive fishery is
to be found on the coast of Venezuela. This also
dates back before the time of Columbus. The
most famous banks are on the sides of the island
of Margarita which has thus received its name.
About 400 sailing boats of from three to fifteen tons
are employed (according to Cattelle), and in 1906
practically 2000 men were engaged in the fishing.
The Government of Venezuela has given rights and
concessions to individuals in return for which it is to
receive 15 per cent. of the net profits. The species
of pearl oyster fished is Margaritifera squamulosa,
and it resembles the Ceylon pearl oyster. The shell
is very thin and the mother-of-pearl obtained in
these fisheries is worth only a fraction of the value
of the pearls.

We have not exhausted by any means the pearl
fisheries of the world, amongst which may be men-
tioned, also, the Pacific island fisheries, the fisheries
of California, the African coasts and the Mediter-
ranean. We shall conclude by a reference to the
fresh-water pearl fisheries which are of importance,
in the rivers of Kurope and America.

The fresh-water pearl mussel of Europe is Mar-
garitana margaritifera. It has been fished in Great
Britain from the time of the Romans, and in the

90 PEARLS (cH.

middle of the 18th century large quantities of pearls
were obtained from these shellfish in the river Tay.

The Scotch pearl fishery was stimulated again in
1860. The Irish fishery seems to have died out—the
shellfish being much less common now than formerly.
In 1906 the value of the pearls collected from the
shellfish in the British Islands was put down as
£3000. No elaborate system of boats and dredges
is used and probably all the shellfish are obtained by
wading and feeling for the individual specimens.

On the continent the fishing has been carried on
for a long time in the rivers of Finland. The pearls
find their way chiefly into Russia. The fresh-water
pearl mussel is also very common in the rivers of
Germany and Bohemia. Quite recently the origin
of pearls in these shellfish has been investigated
in great detail by the Germans: reference will be
made to their discoveries in a later chapter. The
fishing has been very regular and carefully looked
after in these countries. The rivers are inspected in
springtime and the fishing takes place in summer.
At the same time the recent pollution of water by
factories has caused the usual decrease in the number
of mussels. Pearls have also been obtained from the
French rivers and in fact from many others in Europe
which lack of space prevents us from mentioning.

The total value of pearls obtained on the con-
tinent of Europe in 1906 was about £20,000.

vil] PEARL FISHERIES OF OTHER LANDS 91

In America the fishery for fresh-water pearls is
of greater importance, the value of pearls and shell
together for 1906 being about £200,000. The fishery
dates back to the time of the ancient inhabitants
and remains of the shells are found in Indian mounds.
The modern fishery was stimulated into growth in
1857 by the finding of a very fine pearl weighing
93 grains at Notch Brook near Paterson (New Jersey).
It was sold to the Empress Eugénie for 12,500 francs.

The news of this discovery had an effect, similar
on a small scale, to the discovery of gold. The
American pearl mussels are found in rivers over
a very wide area of the States and Canada. For
further information reference should be made _ to
the literature of American writers who have treated
this subject in considerable detail.

CHAPTER VIII

THE ORIGIN OF PEARLS

WHATEVER be the cause of pearl formation in the
different molluscs in which pearls are found, they are
always pathological products. It may seem strange
that the beautiful gems now so much in demand

92 PEARLS [cH.

for ornamentation are but calcareous deposits, due
to some irregularity, some perverted growth, or some
abnormal process: but such is the case. There is,
however, no lack of romance in connection with
pearls, both in the fancies of the East and traditions
of the West, and even in the sober science of to-day.

The Hindoos, whose attention must of course have
been drawn very early to these glorious objects, con-
sidered (as in fact they do now) that the pearls were
consolidated drops of dew. They believed that the
pearl oyster came to the surface and opened wide
its two valves. Drops of dew fell inside and solidified
in consequence of the heat of the sun’s rays. Pliny
must have known of the fiction of the Hindoos when
he related the tradition that the pearl oyster rested
during the night with its valves open and received
the drops of dew. The very quality of the pearls,
their whiteness and their brilliance, were all sup-
posed to be related to the condition of the dew-
drops that had been so transformed.

Many a beautiful story has been woven around
these beliefs. The pearls are Nereids’ tears—again,
they are dew-drops falling into the sea from over-
hanging leafy boughs. Other less fanciful ideas and
theories have been promulgated from time to time,
and every new account of the origin of pearls is intro-
duced or prefaced by the enumeration of all previous
theories.

vit | THE ORIGIN OF PEARLS 93

Since this little book is written for those who are
not likely to consult a long series of original works,
the author may be pardoned for giving yet another
similar compilation.

Author Theory of cause
Aelian Flashes of Lightning.
Rondeletius (1554) Parasites and concretions.
Redi (1671) Grains of sand.
Various 16th cent. writers Eggs of the mollusc.
Reaumur (1717) Solidification of shell forming fluid.
Home (1826) A modified view of the egg theory—i.e.
abortive ova.
Filippi (1852) A worm parasite, Distomum.
Kiichenmeister,

Von Hessling, ; (1856) Parasites, sand, eggs.
and Meckel J

Moebius (1857) Entozoa.
Kelaart (1857-59) Sand, diatoms, eggs and parasites.
Garner (1863) Distomum parasite.
Comba (1898) Parasites.
Dubois (1901, 1903) Parasites.
Jameson (1902) Parasites.
Herdman and! (19906) Parasites, ete.
Hornell }
Seurat (1902) Parasites.
Giard (1903) Parasites.
Boutan (1904) Parasites.
Rubbel (1911) Shell substance
Jameson (1912) Shell repair substance and perhaps

parasites.

It will perhaps be startling even to scientists, who
have not read up the older biological literature, to

94 PEARLS [cH.

see how often the theories of sand grain and the
parasite causation have been brought forward in
the past. The grain of sand theory dates back
much further, too, than Redi, 1671.

Whilst this view dominated our older text books,
and particularly school books and popular works,
until quite recently, the idea that a parasite pro-
vided the stimulus for pearl formation has been re-
peatedly put forward since 1554. The older workers
did little more than make guesses, but Filippi as far
back as 1852 actually discovered a parasite as cause
in the fresh-water mussel. It will be seen, therefore,
that all the workers of the last ten years who have
pushed the research upon pearl formation as far as
fresh advances in biological technique would allow,
have had at least numerous helpful suggestions left
as a legacy by their predecessors.

We shall only refer in detail to one or two of the
causes tabulated. First let us look at the old grain
of sand theory, which modern writers have tended to
throw over completely, notwithstanding the fact that
Herdman and other workers have recorded sand
grains as occasional nuclei in pearls.

This theory assumed that grains of sand found
their way between the shell and the mantle of the
molluse and irritated the latter so that it responded
by coating the invading object with layers of pearly
substance. This certainly does take place sometimes,

vill] THE ORIGIN OF PEARLS 95

and a similar process follows the introduction by man
of small objects between shell and nacre-secreting
tissues. As we have seen, however, in another place
(p. 53) the pearly objects so formed are not really
pearls, but blisters. The Chinese, for example, insert
rows of images of Buddha between the mantle and
shell and allow them to remain until coated with
nacre. There are, however, a few cases on record
where free pearls have been found with sand grains
as nuclei, consequently we must assume as an occa-
sional true cause of pearl formation—the minute sand
grain. Probably this cause is of rare occurrence and
of little importance.

Now let us look at two very important theories,
and first at that which regards the entrance of a
parasite into the shellfish as the cause of pearl forma-
tion. We have seen that the structure of pearls is
intimately related to the structure of the mollusc
shell. The latter is secreted by a layer of cells which
bounds the surface of the mantle. Now it must be
borne in mind during the following study that pearls
are formed inside a little sac of cells. This “ pearl
sac’’ was recognised by von Hessling in 1858. It is
composed of a single layer of cells, which are very
similar to those bounding the surface of the mantle
against the shell (see fig. 9). In fact, just as the
mantle cells secrete shell substance of one king or
another, so do the pearl sac cells secrete the layers

96 ' PEARLS [CH.

which build up the pearl. It will be quite clear then
that if we can say definitely in every case how and
why the pearl sac has been formed, we shall have
solved the problem of the origin of pearls.

The Italian scientist, Filippi, is usually credited as
being the originator of the view that the nucleus of
pearls is an entombed parasite.

This investigator, whilst examining fresh-water
mussels (Anodonta—quite common in our ponds and
streams) in the royal parks near Turin (1852) was
surprised at the large number of pearls found therein.
At the same time the abundance of pearls was
attended by the presence of large numbers of a
parasitic flat worm (Distoma duplicatum). Filippi
next examined the pearls, which were of various ages
and sizes, and found always an organic nucleus. It
was apparently impossible to recognise definitely in
the entombed organic matter the form of the worm,
but arguing from the abundance of both pearls and
worm parasites (and the organic nuclei) Filippi did
not hesitate to suggest that the worm parasites had
caused pearl formation. Later, Filippi recognised
certain parasitic remains in other pearl nuclei—re-
mains of other species of worms.

In 1856, Kiichenmeister found in both Anodonta
and Unio (both common shellfish of fresh-water ponds
and streams in the British Isles) the remains of an
arthropod in the nuclei of pearls.

Vill | THE ORIGIN OF PEARLS 97

In 1857, the German zoologist Moebius took up
work on pearls and penetrated much more deeply
than his predecessors into the mysteries of pearl
formation.

He did not content himself with the fresh-water
pearls from his own country but examined those
from Indian and American molluscs. Once more, the
general absence of the grain of sand as nucleus was
noted, and yet again the presence of a worm parasite
was put on record. We find about the same period
that Dr Kelaart, a medical officer in Ceylon, who
was one of the first workers on the Ceylon pearl
oyster, repeated the statement that minute parasitic
worms were the cause of pearls. . This time—that
they were the cause of the true oriental pearls.
Numerous investigators followed, but there is un-
fortunately no room here for a history of their
searchings and theories, and we must skip over the
intervening years until we come to the much more
definite and recent work of Dubois, Diguet, Jameson,
Boutan and Herdman. So far, it will be seen that
workers had set themselves to discover the contents
of the nuclei of pearls, and it may be admitted that it
is by no means an easy task to make out in sections
what the organic débris of such nuclei might once
have been.

Now, though we are at present dealing with the
history of the parasite theory, it will be of interest to

-

D. /

98 PEARLS [CH.

note here that objections of remarkable force were
made to it by von Hessling, who wrote in 1858.

The importance of his statements, however, is only
just being recognised. Von Hessling believed that in
rare cases foreign bodies of various kinds getting into
the mollusc might provoke pearl formation, but he
regarded as the chief cause some sequence of events
intimately connected with the phenomena of shell
growth. He makes, in-this connection, the very note-
worthy statement that the nucleus of pearls is very
often formed of granules of the substance which
forms the external layer of the shell—the horny
pervostracum.

Reference will be made to this observation later,
and it will then be seen how closely this agrees with
some recent views. The modern period of activity in
pearl research may for our purpose be taken as dating
from about 1897. In 1899, Léon Diguet described the
pearl sac, already seen by von Hessling, and this was
supposed to secrete nacre round the remains of a
parasite which then formed the nucleus of the
pearl.

In 1901, Raphael Dubois published a paper on
pearl formation in Mytilus (the common edible
mussel), his specimens being taken from the French
coast, and during the same year Jameson followed
Dubois in working at the same problem at the same
place—Billiers in Brittany.

vul| THE ORIGIN OF PEARLS 99

His paper followed in 1902, and confirmed the
discovery of Dubois. Both these workers definitely
established the fact that in the edible mussel from
Billiers, pearl formation was caused by larval worms
which were parasites in the shellfish. Moreover, the
larvae were recognised as the young of the flatworms,
known as trematodes (related to the familiar species
which occurs in the liver of sheep and causes liver
rot). Dubois simply followed up the methods of
previous investigators. Jameson gave a much more
detailed account of pearl formation, and pointed out
the great importance of discovering the method by
which the larval parasite caused the formation of the
pearl sac. In addition to this he attempted to trace
the young parasite to the adult worm. Like many
other parasites, this worm requires several hosts in
order that it may live its normal life. Just as the
trematode parasite (the liver fluke) of the sheep
requires two hosts, a pond snail and the sheep, and as
the well-known malaria-causing parasite requires both
mosquitos and man, so does the worm parasite in the
mussel require at least one other host. Jameson
attempted to piece together by experiments this life-
history, and came to the conclusion that the adult
form lived in a bird, the common Scoter, which feeds
on the mussels and destroys large numbers of them
at Billiers. His investigations gave the following
interesting life-cycle for the parasite.

bo

100 PEARLS [CH. VIII

The adult worm (which he considered to be Leuci-
thodendrium somateriae) lives in the Scoter (Oedemia
negra) and there produces its eggs. The eggs pass
out of the bird to the external world, where probably
most of them die. The fortunate ones, however, either
themselves become, or give rise to a tiny free-swimming
larva, which reaches the bivalve, 7’apes, or else the
common edible cockle (Cardiuwm edule). In one or
other of these molluscs the eggs or larvae commence
the first part of their life and develop into spherical
cysts. From the walls of these cysts other larvae are
formed. These leave the cockle (or Tapes) and if
fortunate eventually reach a mussel.

They bore into the mussel and come to rest in its
tissues, and round them an epithelial sac of cells may
appear. Now, if the mussel should be eaten by a
bird—the Scoter—the larvae reaching their final host
develop into the adult worm, and that is the end of
the story.

If, however, the epithelial sac is formed and the
mussel does not fall a prey to some predaceous bird,
the trematode larva dies and round its remains the
epithelial sac secretes a mausoleum of pearl. A more
startling story could hardly be imagined, but most
of the life-cycles of animal parasites are extra-
ordinarily exciting. We may tabulate the stages as
follows :

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102 PEARLS [CH. VIII

With regard to the pearl sac which appears around
the worm larva in the mussel, Jameson accounted
wrongly for its origin in 1902. He states that “This
epithelium appears to arise quite independently of
the outer epidermis, and is no doubt due to a specific
stimulation on the part of the parasite, as other
parasites, e.g. sporocysts, cestode larvae, etc. are not
surrounded by such a sac.” He continues by saying :
“At first a few cells appear which proliferate and
arrange themselves along the wall of the cavity....
From the first these cells are basally continuous with
fibres of connective tissue. Their transformation into
the pearl sac is a gradual one, and every step can be
traced in sections of the parasites 7 setu.” It was
the Frenchman, L. Boutan, in 1904, who continued the
investigation of pearl formation in the edible mussel
(Mytilus) and completed the story by describing how
the pearl sac was really formed by the parasite.

Boutan states that the parasitic larva in the
common mussel reaches the space between the shell
and the mantle of the mollusc. It then comes to lie
in a little pit or depression in the epithelium of the
mantle (diagram, fig. 9 a).

Gradually the parasite sinks deeper and deeper
(fig. 96 and ¢), the epithelium of the depression
becomes a little flask and finally a sac just com-
municating with the surface by a small opening. In
the end, the sac becomes cut off altogether, and we

Fig. 9. Diagrams (modified from Boutan) showing formation
of pearl and origin of Pearl Sac in Mytilus. §., shell. Epi., shell-
secreting epithelium of mantle. Conn., connective tissue of mantle.
P., parasite. Pe., pearl. Pe. Sac, pearl sac.

- 104 PEARLS [CH. VIII

have a parasite lying in a little sac (the pearl sac) of
epithelium which is decidedly the same as the shell-
secreting epithelium of the mantle, because it was
once continuous with it (fig. 9d). This pearl sac
will have already commenced secreting layers of
shell-like substance round the parasite which has
been the cause of the sequence of events leading to
its formation.

Thus pearls are formed in the common edible
mussel. This method, however, is not to be supposed
for a moment as applicable to other molluscs without
experimental evidence. As a matter of fact, it is not
the only method of pearl formation even in Mytilus.

Now let us turn to the Ceylon pearl oyster which
produces such valuable pearls and see what processes
are involved there.

The problem of the origin of the valuable oriental
pearls is obviously of greater economical importance
than that of the Mytilus pearls. The discussion of
the theories brought forward will be given in two
separate sections, for if the description of pearl forma-
tion in the fresh-water mussel is interpolated in the
middle of our account of the Ceylon pearl oyster
we shall be following the discoveries in their proper
sequence.

In 1902 the British Government sent to Ceylon
a scientific commission (consisting of Prof. Herdman
and Mr J. Hornell) in order to report upon the

Fig. 10. Section of larval worm (Ces-
tode) parasitic in Ceylon Pearl Oyster. (After
Herdman. )

Fig. 11. Tetrarhynchus wunionifactor.
Practically young adult stage of one of
the parasitic worms of the Pearl Oyster.

106 PEARLS [cH.

condition of the famous pearl banks of the Gulf
of Manaar, which, notwithstanding numerous bad
years, have yielded much profit to the Government
of Ceylon. The results of their investigations’ are
extremely valuable, and it must be remembered
that the primary object of the expedition was to
report upon the conditions of the pearl banks, the
distribution of the beds of pearl oysters and the
influences affecting their life and prosperity.

However, in addition to this work, Herdman and
Hornell also examined many pearl oysters and such
pearls as were obtainable for the purpose of deter-
mining the cause of their formation.

Obviously they were well acquainted with the
numerous theories of their predecessors when they
first went out to Ceylon, and consequently when in
March 1902 they noticed numerous white larvae
(fig. 10) parasitic in the “liver” of the pearl oyster,
they devoted some attention to their occurrence and
nature, and came to the conclusion that these para-
sites were the young of cestode worms (the most
familiar cestode worms are the common tapeworms
of man, the dog, etc.), and subsequent work showed
that some at least of them were the larvae of a worm
that occurs frequently in Elasmobranch fishes and is
called Tetrarhynchus (fig. 11).

1 Given in a Report to the Ceylon Government, published by the
Royal Society, in 1903-6.

vill | THE ORIGIN OF PEARLS 107

Now, sections of the Ceylon. pearls in situ differ
considerably from those of Mytilus pearls, and in two
ways. The pearl sac is not nearly so distinct, and the
nucleus of the pearl is much smaller and looks
different. In several cases Herdman could not find
any nucleus at all.

We have already seen that there are two kinds
of pearls in the Ceylon pearl oyster, “cyst” (or
parenchyma) pearls and “muscle” pearls, the latter
occurring in large numbers near the insertions of the
muscles. The muscle pearls were never believed by
Herdman to have been caused by parasites. Herdman
and Hornell stated that it was probable that these
pearls were formed by the deposition of calcareous
matter round some minute calcareous particles or
calcospherules. The origin of the calcospherules
themselves was guessed at by Southwell, who stated
that they were almost certainly depositions from the
blood.

From what we have already seen, we should expect
an epithelial sac to be present to deposit this cal-
careous matter. From whence does this come if not
brought in by a parasite? Herdman and Hornell,
noticing that the muscle pearls were formed very close
to the surface of the mantle, found no difficulty in
presuming that the epithelial cells on the surface of
the mantle might migrate inwards to the source of
irritation. So much then for the muscle pearls to

108 PEARLS [CH. VIII

which we shall return later. Suffice it to say that
Herdman and Hornell believed them to be formed
owing to internal causes and not to any parasite or
other body of external origin.

With regard to the other really fine oriental
pearls, Herdman and Hornell came to the conclusion
that the chief agent concerned in their formation was
the tapeworm larva, which occurred so frequently in
the pearl oysters. The oriental pearls are of course
like all others formed by the activity of a pearl sac,
and Herdman recognised the great resemblance of
this to the outer shell-secreting epithelium. The
origin of the pearl sac has, however, never been
observed in the Ceylon pearl oyster, but Herdman
thought that the parasite boring into the mollusc
might carry in certain epithelial cells from the
surface.

What is the life-story of this parasite which occurs
in the pearl oyster? It must be confessed that so
much doubt exists concerning the relation of the
encysted larvae to both the pearls and the adult
tapeworms that the technicalities are beyond the
scope of this little book. The conclusions of Herd-
man, Hornell and Shipley (who described the para-
sites found in the Ceylon pearl oysters and fishes)
can be expressed in the following form :

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110 PEARLS (CH.

It will be seen that there are two possibilities.
If one be taken there are two hosts only for the
parasite. In the other case there are three hosts.
In this latter, the worm larva has first to enter a
pearl oyster (in which it passes its first days). The
pearl oyster must then be eaten by a file fish or
other Teleostean in order that the second stage of
life of the parasite may be safely negotiated, and
finally a third host, the ray, must be reached, by the
annihilation of the file fish:—truly an interesting
picture of the dependence of animals one on another.
If these theories are correct, it is therefore neces-
sary for pearl production to be assured to have pearl
oysters, worm parasites, file fishes and the rays, pre-
sent together in the same locality.

As a matter of fact it is very probable that the
file fish is only an accidental host and that the direct
passage of the larva from the pearl oyster to the ray
is all that is required’.

Now, are we to consider that the majority of fine
oriental pearls have been produced by the influence
of worm parasites or not? Jameson doubts the
cestode worm theory, although in 1902 he stated
that he himself found worm parasites in decalcified
and sectioned pearls from the Ceylon oyster. Let us

1 Jameson believes that there are three distinct species of parasites

encysted in the pearl oyster, but in each case the adult worm is to be
found in some fish that feeds upon the oysters.

VIII | THE ORIGIN OF PEARLS 114

leave the Ceylon pearl oyster for a while and turn to
the most recent scientific work on the fresh-water
mussel in Germany.

Rubbel, working at Marburg, has once more
shown how often the older scientists came near
to the solution of problems not finally solved till
to-day.

According to the investigations of this worker
the fresh-water mussels (Wargaritana margaritifera)
examined by him contained few parasites that could
give rise to pearls. Parasites were, moreover, not
found to be the cause of pearl formation in this
shellfish. The nuclei of the pearls consisted of par-
ticles of a yellow-brown substance, that was strongly
refractive. This substance could be found scattered
in the connective tissue of the mantle and also in the
shell-secreting epithelium of the mantle. Further-
more it seemed to be related to the substance of the
outer layer of the shell, i.e. the periostracum. In
short, we are reminded of the views of von Hessling,
put forward in 1859.

In order to understand fully the mechanism of
pearl formation, Rubbel first made experiments to
determine what the outer shell-secreting epithelium
of the mantle could do in the way of repairing broken
shells or regenerating pieces of shell that were re-
moved. He discovered that the nacre-secreting
epithelium, normally secreting the mother-of-pearl

112 PEARLS [CH. VIII

layer, had the power or potentiality of producing all
the other layers of the shell.

The pearls, however, as we have already seen,
consist of some or even all of the layers of substance
which form the shell. They sometimes consist only of
periostracum and are yellow or brown and horny
looking in appearance. Most pearls, however, consist
of concentric layers of periostracum, prismatic sub-
stance and nacre, with another layer present in
places—the hypostracum. These layers may alternate
irregularly (figs. 6 and 7).

The yellow-brown granules, referred to above as
being akin to the substance of the periostracum, are
to be found in the outer epithelium (fig. 12 @).
Rubbel believes that some of them are dissolved ;
others, however, remain and stimulate the epithelium
in some way so that they become surrounded with
cells directly continuous with the outer epithelium
(fig. 12a). There are many points of resemblance
here with the effect of parasites as described by
Boutan, but it will be noticed that the granules
(internally produced) are the cause, and that they do
not lie outside the epithelium. The cells surrounding
the granules secrete new substance round this nucleus,
and we may already speak of the little body so formed
as a young pearl. Gradually the epithelial pearl sac
with its contained pearl breaks away from the outer
epithelium (fig. 120), until finally it is completely

Fig. 12. Figures showing the development of the Pearl Sac
according to Rubbel (modified from Rubbel). Per., periostracum-like
substance forming the nucleus of the pearl. Epi., epithelium of
mantle. Pe. Sac, pearl sac. Pe., pearl. Conn., connective tissue
of mantle.

D. 8

114 PEARLS (oH.

separated and lies free in the tissues (fig. 12¢). So
the pearl formation in this fresh-water mussel com-
mences actually in the outer epithelium and is caused
by a product of the mollusc itself. Thus we arrive
at a very important point, which is that there is no
obvious difference between “muscle pearls” and other
true pearls, for both are formed round nuclei which
are products of the shellfish. Any difference in
structure may be simply due to their difference in
position.

The pearl sac appears to possess the power of
secreting all the various kinds of shell substance, one
after the other. Parts of it may even be secreting
one kind of substance whilst other parts secrete
another. What determines the character of the sub-
stance to be secreted is quite unknown.

Thus we have dealt with a second method and
cause of pear] formation, which has now been demon-
strated by Rubbel to be of frequent occurrence.

In conclusion let us return once more to the
oriental pearls from the Ceylon pearl oyster. We
have seen that Herdman recognised various causes,
and that the muscle pearls were supposed by him to
be formed round a substance which was a product of
the shellfish itself. The chief cause, however, in the
case of cyst pearls was supposed to be a cestode
parasite which was found infecting the oysters in
abundance.

VII | THE ORIGIN OF PEARLS Ws

Jameson examined a very large number of oriental
pearls and published an account of his results last
year (1912) which, though written without any know-
ledge of Rubbel’s paper, agrees in a remarkable
way with this author’s conclusions for the fresh-water
mussel. This renders it extremely probable that
the method described above, and discovered by
Rubbel, is of very general application, and is the
chief cause of pearl formation in many other mol-
luscs.

Jameson does not call the layers seen in the pearl
by the names of similar layers in the shell. He
recognises the resemblance to repair substances of
regenerated shell, and so uses the terms “granular
repair nacre,’ “columnar repair substance,’ and
“amorphous repair substance,’ for the nacre, pris-
matic substance and periostracum respectively.

The formation of the pearl sac has, however, not
even yet been traced in the Ceylon pearl oyster.
From the evidence of structure Jameson concludes
that the tapeworm cause is of little importance in the
case of Ceylon pearls, and that whilst sand grains and
other foreign particles or organic bodies may form
the nucleus of these pearls, a foreign nucleus is prob-
ably exceptional. The factors giving rise to the pear]
sacs have therefore yet to be discovered.

We would suggest as probable that eventually
a sequence of events similar to that observed by

S—2

116 PEARLS [ CH.

Rubbel in the freshwater mussel, will be discovered
in the case of the Ceylon oyster.

Thus we have seen how pearls may be caused by
foreign bodies (sand grains, parasites, or other objects)
or by internal products of the pearl-producing mollusc.
As Dubois, in a recent summary of the matter, puts
it: “Il existe deux catégories de margaritose ou
maladie perliere; lune parasitaire et l’autre non
parasitaire.”

The importance of the causes referred to varies
according to the species of shellfish in which the
pearls are found, but whichever cause we look into,
we find something of the romance of science, a know-
ledge of which cannot fail to increase the value of
the pearl as a gem, in the eyes of any enlightened
owner.

CHAPTER IX

PEARLS IN JEWELLERY AND TRADE GENERALLY.
ODD FACTS

Ir will have become evident from the preceding
chapters that the pearl is still retaining its hold in
the fashionable world of the 20th century. As a
matter of fact, the value of pearls has steadily

Ix] PEARLS IN JEWELLERY, ETC. M7

increased in the last decade, notwithstanding the
opening of new fishing grounds. The pearl industry
(speaking only of the actual fishing itself) plays no
small part in the economics of the world, and the
following table, from Kunz and Stevenson’s volume,
showing the number of fishers and the approximate
value of the products found by them in 1906, supports
this statement.

Local value Local value
Pearl fishers of pearls of shell
Asia. £ £
Persian Gulf 35,000 800,000 22,000
Ceylon 18,500 240,000 8,000
India 1,250 20,000 19,000
Red Sea, Gulf of Arabia,) .
and African Coast f HeG00 eet opm
China, Japan, Siberia 20,000 80,000 10,000
Europe.
British Isles 200 3,000
Continent 1,000 20,000 600
Pacific Islands.
South Sea 4,500 25,000 100,000
Australian Coast 6,250 90,000 240,000
Malay Archipelago 3,000 60,000 160,000
America.
U.S.A. rivers 8,500 130,000 70,000
Venezuela 1,900 55,000 2,000
Mexico 1,250 42,000 40,000
Panama 400 8,000 15,000
Various 1,000 15,000 5,000

It would be quite impossible to make any state-
ment as to the value of pearls, for so many details

118 PEARLS (cH.

enter into the question. It is primarily judged by
size or weight, but this may be modified altogether
by the shape, lustre, colour and perfection of the
pearl generally. One or two details of interest may,
however, be given. In the first place, the value of
pearls is reckoned not on the weight, but on the
square of the weight.

The pearl grain, which is a fraction of a carat, is
the unit, and a base price is the value of this unit.
What the base price may actually be, we shall not
attempt to estimate. If, however, the base value of
a l-grain pearl is taken as being 20s., then the value
of a 2-grain pearl would be 2 x 2.(20s.)=£4. <A
5-grain pearl would be worth (5 x 5). 20s. = £25.
Even this method does not hold good for very large
pearls of perfect lustre. The carat and grain both
vary in the different countries in which they are used,
although a very representative circle of pearl mer-
chants is now upholding a metric system carat which
equals 200 milligrammes.

So far as the value of mother-of-pearl shell is
concerned, the following figures may be given. The
values are, however, always liable to much fluctuation
and these figures are not of quite recent date. Port
Darwin shell (North Australia), £8—£9. 10s. Od. per
cwt.; Queensland shell, £8—£11 per cwt.; West
Australian shell, £8—£9 per cwt. (1910).

Reference has been made in the chapter on

Ix | PEARLS IN JEWELLERY, ETC. 119

pearls to the manufacture of artificial pearls. As
the price of pearls has advanced, very much care and
ingenuity has been shown in mounting and altering
pearls which have defects. Surfaces may be restored
by scratching or roughening. Badly coloured pearls
may be bleached, but this is a dangerous method and
the pearls soon deteriorate after such treatment.

Skinning (or peeling) is a very well-known opera-
tion. It consists in removing the outer layers or
laminae from pearls which are not quite perfect. This,
however, presupposes the presence of better layers
underneath The result may be a very much enhanced
value or the reverse. Skinning requires great care
and it is performed under the magnifying glass with
steel files.

The drilling of pearls is another delicate operation,
although the introduction of special apparatus has
increased enormously the number that can be handled
in a given time. Much skill can be shown in choosing
the point where the hole shall be drilled. Small
defects can be hidden in this way just as imperfections
in shape can be toned down by careful mounting.

Pearl stringing is another art. Hach pearl on a
string should be secured by knots so that breakage
of the cord will not be followed by a scattering of
precious gems. The cord used is of the very best
silk, and “restringing ” should take place every 3 to 6
or 12 months according to the wear that takes. place.

120 PEARLS [cH.

Only this Christmas (1912—13) there appeared in
the. press a story of the “dying” of pearls. Many
similar stories have appeared from time to time, all
more or less sentimental. As, however, pearls do
not live, they cannot die. Moreover, pearls well
treated practically do not change in appearance. As
a matter of fact, the gem is at its very best when
it is first abstracted from the shellfish in which it
has been formed. Pearls are sometimes stained
yellow by exudations from the skin, especially if
the latter is unhealthy. The same staining effect is
produced bysulphurous or other polluted atmospheres.

This change in colour, or lustre, may sentimentally
be described as “death,” but the statement certainly
has no real meaning. There seems also to be a
strange lack of evidence supporting the common
belief that some individuals can restore the lustre
of pearls by wearing them.

There are, of course, various methods of cleaning
pearls and restoring them, but perhaps it will be
advisable to refrain from giving them here. Good
pearls require careful handling and had better be
left in the care of specialists.

This little book would be incomplete if no mention
were made of some of the famous pearls in the world’s
history, and probably first in this respect must be
placed the gems worn by Cleopatra.

Almost everyone has read or heard of the wager

Ix] PEARLS IN JEWELLERY, ETC. 121

made by Cleopatra with Mark Antony and its sequel.
The story is both antique and we regret to say absurd.
Cleopatra is supposed to have dissolved one of the
pearls suspended from her ears (a pearl, the value
of which has been estimated at £60,000!) in wine,
and to have drunk the solution. Chemically, this is
quite impossible, for the organic matter would cer-
tainly not dissolve, and very little if any of the
inorganic would have been affected even by vinegar
in the time. She might of course have swallowed
it as a pill! The other pearl, its fellow, is supposed
to have been cut in halves and placed in the temple
of the Pantheon.

Charles the Bold, Duke of Burgundy 1433—1477,
is said to have possessed a very large and valuable
pearl. The pearls of Mary Stuart are also to be
reckoned amongst the most famous of the time. They
were said to be the most beautiful in Europe.

Of course many of the most precious pearls have
not been brought to the publicity of the auction room
and may still exist in the East. Reference may be
made here to the wonderful Peacock Throne built by
the same oriental king who raised the Taj Mahal.
Very many pearls were used, amongst which was
a choice gem weighing 200 grains. The total value
of the jewels was estimated at £12,000,000, but the
present value is much less, probably somewhere near
£2,000,000. Perhaps the most costly ornament in

129 PEARLS [cH.

the world is a shaw! or carpet of pearls possessed by
the Gaikwar of Baroda. The value of this has been
put down as over £1,000,000.

Of the very large and fine pearls often referred to
by writers, two may be mentioned here, the Hope
Pearl and La Pellegrina. The last-named was one of
the most wonderful pearls in the world. The weight,
1114 grains, was extraordinary for a perfectly spheri-
cal pearl of matchless lustre. It was owned by a
Russian and is said to be still in Moscow, although
the writer thinks that some doubt exists with regard
to this.

The Hope pearl belonged to a London banker. It
is supposed to be the largest pearl known in the
world and weighs 1800 grains or roughly 3 ounces.
It is, however, not spherical, and is more correctly
a baroque. It was sold at Christie’s in 1886 and is
now valued at £9000.

No one who has visited and really knows Naples,
can have failed to have seen something of the cameo
industry. Cameos are of course not made from
pearls, but as they are carved from mollusc shells
and depend upon the layers that we have referred
to so many times, it will not be out of place to
mention the industry here.

The shells used are chiefly univalve coiled shells
related to our common whelk, but they come usually
from tropical seas. The chief species employed are

ix] PEARLS IN JEWELLERY, ETC. 123

Cassis tuberosa Linn., Cassis cornuta Linn., and the
“conch” shell of the West Indies—Strombus gigas
Linn. The latter is a very large shell but is not so
valuable as the others. Large quantities were in
former days imported into Liverpool from the Ba-
hamas, but the writer can get no evidence of the
continuation of this traffic. The manufacture of
cameos consists in carving away certain of the sur-
face layers of the shell. The deeper layers are
differently coloured. Consequently an engraving
results, in which the picture stands out on a back-
ground of another colour. In the case of the conch
shell, the cameo is yellow on a beautiful red. The
Cassis shells give white on an orange or golden
background.

It may be surprising to most readers of this little
book to hear that pearl-like structures occur some-
times in plants. It may be quite incorrect to speak
of them as pearls, but some of them, especially rare
specimens from the cocoanut, are said to resemble in
colour and appearance the real pearls from the sea.

It appears, however, most difficult to get any con-
clusive evidence about these calcareous concretions.

Riedel (according to Professor Korschelt) is sup-
posed to have found one of these in a cocoanut in
1886 whilst in North Celebes. It was pear shaped
and 28 mm. long. Harley, who made chemical analyses
of the real pearls, examined a supposed vegetable

124 PEARLS [CH.

pearl that came from Singapore. He was very scep-
tical, however, because it resembled rather closely a
pearl from the bivalve Z'rzdacna and its composition
was very different from the constituents of the cocoa-
nut. Calcium is usually deposited in plants as oxalate,
although of course numerous calcareous algae are
known in which calcium carbonate is deposited.

CHAPTER X

THE PEARL OYSTER—THE TRADER—THE MAN OF
SCIENCE—THE CULTIVATION OF PEARL OYSTERS

WE have described the pearl, the pear] fishery,
and the economic and scientific aspects of pearling;
what should be more natural than a combination of
science with the pearl industry? Science is now
such a force in the world that we should expect
it to come to the aid of the pearl] fisher.

Before the jeweller can mount the valuable gems
from molluscs of the sea or fresh water, the fisher
must supply him with the materials for his trade.
This means first and foremost that large beds of
flourishing pearl-producing shellfish are required.
Then, secondly, we require that these molluscs shall

x] PEARLS AND SCIENCE 125

produce pearls in quantity and of good quality.
A prolific supply of shellfish does not necessarily
mean a handsome supply of pearls, and it has been
noted very often in the case of the common mussel
that the molluscs from some beds produce far more
pearls than those from other areas. At the same
time, without the molluscs there will be no possibility
of pearls. Evidently then, the first care must be for
_ the beds of molluscs.

Granted that shellfish of the right kind are
present in abundance, we might turn our attention
to artificial improvement of their powers of pearl-
production. As will be seen in the course of this
chapter it is still the cultivation of the pearl oyster
that requires the first aid from science, and cer-
tainly, so far as Ceylon is concerned, we must agree
with Herdman, who has regarded the condition and
the welfare of natural beds of oysters as a more
important problem than the question of pearl-
production.

It must be confessed that so far science has not
proved a marked success in its application to pearl
industries. This, however, is not the fault of science,
but rather its misfortune, and the latter is no doubt
largely due to our treatment of biology, the science
concerned, in this country.

Economic biology is of modern, very modern
growth, and it has had a severe fight in many places

126 PEARLS [en

for its existence. Pure scientists have for some
reason looked askance at it, and the non-scientific
public has not seen its possibilities, except perhaps
in the one branch of economic entomology. The
chemist, the engineer, and the architect may gain
much practical knowledge in our universities which
directly affects technical work. There is, on the
other hand, a considerable difference between the
biology of most university courses and the biology
of the North Sea Fisheries or the Pearl Banks of
Ceylon. The engineering student is not required
or expected to build mighty bridges immediately
after a university career, but the student of biology
without any practical experience is often expected
to solve most difficult problems and to alter con-
siderably the normal course of nature in a few
months. Added to this, however, we have the extra-
ordinary fact that whilst engineers are appointed
to superintend the construction of government rail-
ways, architects to design government buildings, and
so on, apparently anyone, without any previous
training, may be appointed to take care of our
fisheries. All this means that in our educational
work less interest is shown in providing teaching
facilities which would train the men required. It is
certainly rather surprising that in the country which
sent out the Challenger Expedition, which led the
way in deep sea cable laying, and which reaps a

x | PEARLS AND SCIENCE 127

harvest of many millions a year from sea fisheries,
there is practically only one university where definite
oceanographical and fishery courses are held. If they
were asked for, they could easily be arranged, but
under the present conditions there have been few
posts for scientists trained along these lines and the
demand for the training has in consequence been
small.

Again, the number of students who take biology
as a subject is rather small, because, as a rule, z0o-
logical courses are attended by students who hope to
become teachers in various kinds of institutions, or
to take museum posts. Since, owing to mistaken
notions, or false modesty, zoology does not occupy
the place that it should, in our school curricula, edu-
cational institutions do not require many teachers
with a knowledge of this subject. The fact remains
that considering the income from successful pearl
fisheries, there has been really little demand for
scientific interference, and there have been very few
individuals capable of doing such werk without re-
quiring special training.

It is impossible to say when man first endeavoured
to stimulate the pearl-producing molluscs to form
pearls or to cover with nacre objects inserted inside
them. It is attributed by the Chinese to a native of
Hou-Tchéou-Fou who lived in the 13th century.

The rearing or protection of the pearl molluscs

128 PEARLS [ CH.

is more modern. Strangely enough the commercial
success attending the artificial stimulation of nacre
formation has been greater than that accompanying
the efforts of mollusc rearing. It seems to be very
difficult to maintain the natural conditions favourable
to growth and breeding, and the success which has
attended the cultivation of the edible oyster in parks
and other places, has been conspicuous by its absence
from pearl oyster culture.

in recent years Japan has advanced very con-
siderably in combining the work of oyster rearing
with operative work for the artificial stimulation
of pearl production. The work has been cared for
by both the scientist and the business man, and con-
sists in collecting and cultivating the pearl oysters
of Japanese waters, on grounds suitable for them.
After the shellfish have reached a suitable size, a
bead of mother-of-pearl is introduced in the usual
place between the mantle and shell. This, in the
course of time, produces a pear]-like body—or culture
pearl (Jameson). These culture pearls are not, of
course, real pearls, but still, the industry is of such
extent as to pay its way. It is hoped to produce real
pearls artificially by a modification of the method
employed as above.

Several attempts have been made in Australia to
interfere with the normal course of events in the
pearl oyster industry. The late Mr Saville-Kent,

x] PEARLS AND SCIENCE 129

famed for his studies on the Great Barrier reef,
urged strongly the system of cultivation of the Aus-
tralian mother-of-pearl oyster. He made certain
experiments in Western Australia which showed that
shells could be transplanted to very considerable
distances from their natural habitat.

In 1906 Saville-Kent formed a company—The
Natural Pearl Shell Cultivation Company, Ltd.—for
the purpose of cultivating the mother-of-pearl]
oysters in the Torres Straits. Several thousand large
oysters were laid down in the hope that they would
provide young spat which would settle on the
ground and grow up. Nothing seems to have come
out of this work and the lease was abandoned in
1909 at the time of Mr Kent’s death.

Karlier still than this, another company was at
work in the Torres Straits. This was the “ Pilot
Cultivation Company.” Their purpose (according
to Jameson, who visited the Straits in 1900) was to
transplant undersized mother-of-pearl oysters by
ship to an area in the Straits. The company laid
down over 100,000 undersized shell and three years
afterwards these were fished up. Many thousands
appear to have died, but about 35,000 were taken up,
and it is probable that they realised a considerable
sum. It is only too probable that this was over-
shadowed by the expenses of transplanting and
collecting the shell, and experimentation.

D. 9

130 PEARLS [CH.

Several attempts have been made at one place or
another to raise oysters in tanks or docks so that the
young spat would be saved and could be cultivated.
So far, practically no signs of any success of economic
value seem ever to have been in sight. The nearest
approach to success was the attempt of Mr Haynes
(afterwards the work of a syndicate, the Montebello
Shell Syndicate, Ltd.) at the Montebello Islands.
A tidal pond of considerable extent was made and
several hundred oysters were laid down as breeding
stock. Young oysters did appear, but Jameson con-
siders them not to have been the young of the
breeding stock, but to have been immigrants from
the sea, of another species. Eventually these also
disappeared. So far, therefore, nothing but expense
has resulted from this effort.

There is no doubt whatever, as Jameson states,
that the Government of Australia should very
seriously consider this pearl oyster industry. It can
only be improved by a thorough and detailed in-
vestigation by qualified scientists and pearl]-shellers.

Finally, a glance at the scientific inquiry mto
the Ceylon Pearl] Fishery, the results which followed
and the advice tendered to the Government may give
the readers of this little work some idea of the
problems which have to be faced. It was in the
year 1900 that the Government of Ceylon, after
a period of ten barren years, began to consider

x] PEARLS AND SCIENCE 131

whether it might not be possible to prevent the
recurrence of such periods. Professor W. A. Herd-
man, F.R.S., was selected, on the advice of the
Council of the Royal Society and of Sir Ray
Lankester, then director of the British Museum,
for the purpose of conducting a thorough investiga-
tion of the pearl banks. He took with him as an
assistant, Mr James Hornell, and left England at
the end of 1901 for a visit to the Gulf of Manaar.

During the three months of Herdman’s sojourn
at the island, cruises were made on a steamer fitted
for the investigation and all the principal pearl banks
were examined. Dredging, trawling and diving were
carried out, and the biologists also took part in the
annual government inspection of the pearl banks.

As a result of this expedition the condition of
the pearl banks was made known in great detail.
Collections were made of the animals and plants
living along with the pearl oysters. Some of these
are merely passive neighbours, others are active
enemies or competitors for food. It was necessary
to determine what factors influenced the pearl oysters
in their growth in order, if possible, to arrive at the
causes of failure of fisheries. Herdman’s reports con-
tain a mine of information, and we must say that the
work which the expedition was sent to accomplish,
was carried out thoroughly and successfully.

After Herdman returned to England, Hornell

9—2

132 PEARLS [ CH.

remained in Ceylon to continue the work and was
later (1904) appointed Marine Biologist to the
yovernment.

There is no need to give more than a brief
summary of the chief points of Herdman’s conclu-
sions from his preliminary report (1902) to the
‘Government of Ceylon. They are as follows:

‘‘1. The oysters we met with seemed on the whole to be very
healthy.

2. There is no evidence of much disease of any kind.

3. Aconsiderable number of parasites, both external and internal,
both Protozoan and Vermean, were met with, but that is not unusual
in molluscs, and we do not regard it as affecting seriously the
oyster population.

4. Many of the larger oysters were reproducing actively.

5. We found large quantities of minute ‘spat’ in several places.

6. We also found enormous quantities of young oysters a few
months old on many of the Paars. On the Periya Paar the number
of these probably amounts to over a hundred thousand million.

7. A very large number of these young oysters never arrive at
maturity. There are several causes for this :—

8. They may have natural enemies, some of which we have
determined.

9. Some are smothered in sand.

10. Some grounds are much more suitable than others for feeding
the young oysters, and so conducing to life and growth.

11. Probably the majority are killed by overcrowding.

12. They should therefore be thinned out and transplanted.

13. This can easily and speedily be done, on a large scale, by
dredging from a steamer, at the proper time of year, when the young
oysters are at the best age for transplanting.

14. Finally, there is no reason for any despondency in regard to
the future of the pearl oyster fisheries, if they are treated scientifically.

x] PEARLS AND SCIENCE 133

The adult oysters are plentiful on some of the Paars and seem for the
most part healthy and vigorous; while young oysters in their first
year, and masses of minute spat just deposited, are very abundant in
many places.

“To the biologist two dangers are, however, evident, and,
paradoxical as it may seem, these are overcrowding and over-
fishing. But the superabundance and the risk of depletion are
at the opposite ends of the life-cycle, and, therefore, both are
possible at once on the same ground—and either is sufficient to
cause locally and temporarily a failure of the pearl oyster fishery.
What is required to obviate these two dangers ahead and ensure
more constancy in the fisheries is careful supervision of the banks
by someone who has had sufficient biological training to understand
the life-problems of the animal, and who will, therefore, know
when to carry out simple measures of farming, such as thinning
and transplanting, and when to advise as to the regulations of the
fisheries.

(Signed) W. A. Herpman.”

In Herdman’s further Report of 1904, certain
recommendations were made to the Government as
a result of his inquiry.

He suggested that the dredge should be used
more frequently, to supplement diving for oysters,
and that more attention should be paid to inspect-
ing other regions of the pearl bank plateau than the
known paars. Furthermore, that all young oysters
appearing on certain paars, where they never reach
maturity, should be transplanted to more favourable
grounds. Another important point was that an
attempt should be made to increase the area avail-
able for attachment and growth of young pearl

134 PEARLS [CH.

oysters, by artificial “culching,” that is to say,
scattering dead coral, rocks or rubble on the sandy
bottom adjoining the more important paars.

The following agents were recognised as causing
widespread death of the pearl oysters:

1. Shifting sand, due to strong currents;

2. Voracious fishes, chiefly rays and file fishes;

3. Invertebrate animals, such as boring shellfish,

boring sponges, starfishes and the smother-
ing molluse, Modiola.

At the time of this scientific investigation, it was
seen that certain banks were covered with pearl
oysters and there was a prospect, if all went well, .
of a fishery in 1903. This fishery came off and was
the first for 12 years. The revenue netted by the
Government was over £55,000

The following years, 1904 and 1905, were still
greater successes and record fisheries took place,
giving £71,150 and over £167,000 respectively.

Such was the position, when in 1906 a company
was formed and the Ceylon pearl fisheries were
leased for a period of 20 years at an annual
rental of Rs. 310,000. In addition to this, however,
the company had to undertake to spend from
Rs. 50,000 to Rs. 150,000 annually “on the experi-
mental or practical culture of the pearl oyster and
on the improvement of the pearl banks within the
conceded area, and the maintenance thereon of a

x | PEARLS AND SCIENCE 135

proper breeding stock, or otherwise, in the improve- .
ment and development of the fishery.” Now it must
be noted here that science never advocated the
formation of such a company with the fundamental
mistake of having to pay such heavy charges. The
company had, in fact, agreed to pay the Govern-
ment a rent which was about three times the average
annual revenue! This might have been reasonable
‘f the fisheries of 1904 and 1905 had been certain
to be continued; but there was no evidence that
Herdman’s recommendations had been carried out
to such an extent as to warrant this belief, nor
could it ever have been expected that the scientific
recommendations implied for the future an entire
absence of barren years.

The Ceylon Company of Pearl Fishers, Ltd., en-
tered, therefore, upon a highly speculative concern,
although it is quite possible that they expected
science to pull them through. They were successful
in the fishery of 1906, and another fishery followed
in 1907. Thus the first years of the company were
marked by such handsome returns that a very good
dividend was paid within the first few months of the
company’s existence. In fact, about £50,000 was
paid in dividends (during the first two years) on an
issued capital of £90,000! Since 1907, however,
there have been no fisheries and the company paid
rent to the Government until lack of any prospects

136 PEARLS [CH.

_of a fishery resulted in a re-arrangement of terms
and the termination of the lease in April 1912.

Statements have been made that the company
followed absolutely the advice and recommendations
of the scientific advisers, but it seems quite doubtful
how far from a scientific point of view this was the
case. The recommendations were apparently not
carried out to anything like an adequate extent ;
and sufficient adult pearl oysters to form a breed-
ing reserve were not left at the end of the last
fishery.

So far as I am aware, the points put forward by
Herdman in his report are not in the least disputed,
notwithstanding the years of observation since 1902.
Possibly the part played by voracious fishes in
devastating the oysters was underestimated, but
still Herdman recognised them as being one of the
most serious enemies of the pearl oyster. He laid
great emphasis also on the danger of overfishing
which seems to have been sometimes carried on.
There is absolutely no doubt that this commercial
failure is not attributable to biological science, and
Herdman himself did not advise the formation of the
company.

It seems to the writer that the criticism that the
scientific advisers should have devoted more time to
the study of the mechanism of pearl formation is
quite unfair. What was required from them was a

x] PEARLS AND SCIENCE 137

study of the pearl oyster and the condition of the
pearl banks. Without the oysters, it is obviously
quite impossible to get pearls at all.

Commercial pearl fishing still remains a great
speculation. It will require further very careful
study and much more experiment undertaken in
accord with scientific advice before nature is reined
in or guided along paths suitable to man’s industries.

BIBLIOGRAPHY

Only a few references to literature are given here. More
complete lists can be obtained from the memoirs referred
to below.

General

KorscHeLt. Perlen. Fortschritte der Naturwissenschaftlichen
Forschung, Band vit. 1913.
An exceljent short summary of recent york on pearls and
pearl formation.
Kunz and Stevenson. The book of the Pearl. New York, 1908.
This is a large and very beautiful work. It is the best
book of a general kind that has been published on the subject
and covers a very wide range.
Srurat. L’Huitre Perliére. Paris (1900).
A cheap but quite excellent summary of the subject—
some sections now out of date.

Special

Boutan, L. Les perles fines. Leur origine réelle. Arch. Zool.
exper. gén., 4 sér., T. 2, 1904.
(The origin of the pearl sac in Mytilus is described.)
Dieunt, L. Sur la formation de la perle fine chez la Meleagrina.
Comp. Rend. Acad. Paris, T. 128, 1899.

BIBLIOGRAPHY 139

Dusois, R. Various papers on pearl formation have appeared in
the Comp. Rend. Acad. Paris, T. 133 (1901), T. 138 (1904),
T. 154 (1912).

Fru, F. de. Sull’ origine delle perle. Ubersetzt von Kiichen-
meister. Arch. f. Anat. u. Phys. 1856.

(One of the early interesting papers on the origin of pearls.)

Haruey. Composition and structure of pearls. Proc. Roy. Soc.
London. Vols. 43 and 45. 1888 and 1889.

HerpMan, W. A. Presidential Addresses to the Linnean Society.
Proc. Linn. Soc. London, 1905 and other years.

(Summary of old and new theories of pearl formation and
also the method of artificial pearl stimulation discovered by
Linnaeus. )

— Report on the pearl oyster fisheries of Ceylon. Royal
Society. London, 1903—1906.

(A report of five volumes on the Pearl banks of Ceylon,
and the recommendations of the scientific advisers to the
Ceylon Government. An account of pearl formation. )

Jameson, H. L. On the Origin of Pearls. Proc. Zool. Soc.
London, 1902.
(An account of the origin of pearls in the edible mussel.)
—— Studies on Pearl-oysters and Pearls. Proc. Zool. Soc.
London, 1912.

(An account of the structure of the pearls and shell of the
oriental pearl oyster.)

Russet, A. Uber Perlenbildung u. s. w. bei Margaritana mar-
garitifera. Zool. Jahrb. (Anat. Abt.), 32. Bd., 1911.

(A detailed account of some recent work on the formation

of pearls in the fresh water pearl mussel of Europe.)

GLOSSARY

Abalone. <A name applied to the mollusc Haliotis, or, as it is
called in Jersey, the “Ormer.”

Adductor muscle. A muscle passing across from one valve of a
bivalve to the other, for the purpose of closing the shell (see
Fig. 4).

Arthropod. A segmented invertebrate animal with a more or
less hard external case and jointed limbs (for example, the
Lobster or an Insect).

Baroque. Any pear! of irregular form; the name includes a large
range of varieties.

Baskets. Brass sieves used in Ceylon for sifting apart pearls of
different sizes.

Blister. A structure sometimes incorrectly termed a pearl, but
which in reality is nothing but an excrescence of nacre
attached to the shell. A deposit of nacre round an object
placed between the shell of a mollusc and the mantle.

Blue pearls. Dark coloured pearls of opaque slate-blue colour. _

Bombay pearls. Pearls chiefly from the oriental pearl oyster
(Margaritifera vulgaris) which are fished in the Persian Gulf
and Red Sea and exported through Bombay.

Button pearls. Dome-shaped pearls with one surface almost
plane.

Byssus. The threads secreted by glands in the foot of certain
shellfish, for attachment to hard bodies or to one another.

GLOSSARY 141

Cestode. A parasitic flatworm consisting of a hooked head
(scolex) and a segmented body (proglottides). The common
tapeworm is a cestode.

Cilia. Microscopic hair-like protoplasmic processes from cells,
which usually have the power of vibrating rhythmically.
Cocoanut pearls. Pearls from the oyster or clam of Singapore.
Coelom. A restricted term applied to the body-cavity and other
spaces in certain animals, which are formed in a distinctive

manner.

Conch pearls. Pearls, often pink in colour, from the univalves
Strombus and Cassis.

Conch shells. Univalves of the species Strombus and Cassis
employed for making cameos.

Cyst pearls. True pearls which occur in the tissues of pearl-
producing shellfish, in a pearl sac and away from the shell.

Dead pearls. Pearls with practically only a lustreless and a dead
white appearance.

Dorsal. The upper side of an animal as contrasted with the
lower, or ventral side. The backbone side of vertebrated
animals.

Drilled pearls. Pearls bored for mounting purposes.

Drop pearls. Oval pearls or pear-shaped pearls.

Dust pearls. Very small seed pearls.

Echinodermata (prickly-skinned). A group of marine radially-
symmetrical animals including the starfishes, sea urchins,
sea cucumbers and featherstars. |

Ectoderm. The epithelium bounding the outer surface of an
animal’s body, and its derivatives.

Epithelial sac. A sac composed of epithelium, as, for example,
the pearl sac.

Epithelium. A layer of cells bounding a surface in the body of
an animal, whether external or internal.

Fresh water pearls. Pearls from freshwater shellfish of the
family Unionidae,

142 PEARLS

Haemoglobin. A red pigment found in blood, which plays an
important part in the processes of respiration. Its place is
usually taken by other non-red pigments in invertebrate
animals.

Half pearls. Pearls sawn into halves.

Hinge pearls. Pearls of irregular elongated shapes, found near
the hinge of shellfish from fresh waters.

Hypostracum. The most internal layer in a bivalve shell at the
places where the adductor muscles are attached. It is com-
posed of minute columns set at right angles to the plane of
the shell (see Fig. 2).

Lamellibranchiata. The group of molluscs known popularly as
bivalves and characterised by the possession of lamella-like
gills.

Lingah pearls and shells. Shells and pearls from the Persian
Gulf, often the same kind as the Bombay pearls.

Mantle. Two flaps arising one on either side (right and left) of
the body of a bivalve. Each flap has the same shape as the
valve of the shell against which it always lies. It is composed
of connective tissue with an outer bounding layer of epi-
thelium, and this epithelium on the surface in contact with
the shell is responsible for both shell and pearl formation.

Molluse. A_ soft-bodied, non-segmented invertebrate animal
which typically possesses a hard shell. This shell may be
univalve as in the snails, or bivalve as in the oyster, cockle
and mussel. Sometimes it is reduced and internal, as in
the slugs and cuttlefishes.

Muscle pearls. Small pearls found in the muscular tissue near
its attachment to the shell.

Mytilus pearls. Pearls found occurring in the common edible
mussel (Mytilus).

Nacre. The mother-of-pearl layer which lines most bivalve shells
and forms all or only the outer layers of nacreous pearls.

Naked diving. Diving without special dress, ete.

GLOSSARY 143

Oriental pearls. Pearls from true pearl oysters of the genus
Margaritifera ; applied first to pearls from the Indian seas.

Paar. The banks or shallows in the Gulf of Manaar on which
the pearl oysters live.

Pallial cavity. The space inside a bivalve shell, which is part
of the outer world, and usually filled with sea water or fresh
water according to the home of the mollusc.

Pearl sac. The little sac or bag of epithelium which secretes
the layers that build up a pearl.

Periostracum. The outermost horny layer of mollusc shells.

Petal pearls. Flattened, leaf-like pearls.

Pinna. A bivalve, common in the Mediterranean, from which
pearls are obtained. These pearls have little lustre.

Placuna. The window-pane oyster of Ceylon.

Prismatic substance. The substance of which the prismatic
layer of mollusc shells is composed. It lies just under the
outermost layer of the shell, and on its inner surface comes
into contact with the nacreous or mother-of-pearl layer (see
Fig. 2).

Seed pearls. Small pearls, round or irregular, but only } grain
or less in weight.

Skinning or peeling. The removal of the outer layer of a pearl.

Slugs. Nacreous excrescences ; irregularly shaped pearly masses
from fresh water shells.

Tapes. A bivalve, common off the coasts of England and France.

Trematode. A flat worm which is parasitic either externally or
internally. The most familiar example is the “liver fluke”
of the sheep. Another species causes pearl formation in the
edible marine mussel. .

True pearls. Pearls which are formed in a pearl sac, and which
are found free in the shellfish, without any connection with
the shell. They may not be composed of any nacre. Any,
or all, layers of the shell may be found.

Twinned pearls. Pearls which have come together and then
been coated with layers of nacre (see Fig. 7).

INDEX

Artificial pearls, 64, 118, 127
stimulation as a means of
forming, 66, 128

Baroche pearls, 62
Blisters, 53, 64, 66, 95

Cameos, 122
Ceylon pearl oyster, 12
attachment ground of, 46
classification of, 18
development of, 42
enemies of, 30, 50, 134
external features and shell
of, 18-25
mantle of, 25
muscles of, 27, 29
Colour of pearls, 5, 63
Composition of pearls, 61
Cultivation of pearls, 129

Definition of pearls, 52, 53
Drilling of pearls, 119
“‘Dying” of pearls, 120

Famous pearls, 120

Government commission (Herd-
man’s), 104, 130

Inspection of pearl grounds, 73

Medieval use of pearls as medicine,

Nuclei of pearls, 59, 98, 111

Occurrence of pearl oysters, 12
Origin of pearls, 8, 91, 102

Paars, 46
artificial, 44, 49, 133
Parasites of pearl molluscs, 96,
99
Pearls
references in Classics to, 4, 5
in edible mussel, 15, 98
in plants, 123
references in Scriptures to,
| ge
Pearl fisheries
American, 88
Australian, 13, 85, 128
Ceylon, 2, 10, 68, 130
European, 7, 9, 14, 89
Japanese, 88
Persian, 83

Science and pearl fishing, 125
Separation of pearls, 81
Skinning of pearls, 58, 119
Stringing of pearls, 119

Theories of pearl formation, 93
et seq.

Valuation of pearls, 118
Value of pearl fisheries, 117, 134
Varieties of pearls, 54, 107

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