Deo. 1, 19G0.J THE TROPICAL AGRICULTURIST. 
389 
Pearls are an excretion of super-imposed con- 
centric lamina of a peculiarly fine and dense 
nacreous substance consi>:tiii,tr of membrane and 
carbonate of lime. Tlie question of their origin 
has a special attraction foi the zoologist, since it 
still forms one of the unsolved problems of science. 
Pliny held the belief that they were drops of dew 
or rain which fell into the shells when opened by 
the animals and were then altered by some power 
of the mollusc into pearls. This view obtained all 
over the East, and — strange to say — Columbus 
found the same belief popular among the natives 
of Mexico. Moore thus alludes to it in his poem 
"Peri and the PeFirl " : — 
'' And precious the tear as that rain from the sky 
Which turns into pearls ;xs it falls in the sea." 
At the present, day it is popularly supposed tliat 
all peavis have for a nucleus a grain of sand which 
has become coated with nacre by the animal ; but 
this is simply a conjectnie which lias gradually 
become regarded as a fact. Asa general lule, it 
is some organic substance, whieli behaves in 
tiie same way as epidermis when treated with 
certain chemical re agents. In some districts one 
kind of nucleus seems to be more common than 
another, and this is how the different results 
obtained by observers in different localities 
may be explained T!ie most generally prevalent 
nuclei appear to be the bodies or eggs of minute 
internal parasites— such as Filaria Dintoiiia, Buce- 
phalus, &c. Tl is was pointed out by the late Dr. 
Kelaart, in his Report to the Ceylon Government 
on the Pearl Oyster of Aripo ;" and his obser- 
vations were supported by Humbert, the Swiss 
Naturalist, who accompanied him to the pearl 
banks in 1895. More rt-cently, similar observations 
hav.i been made by Mr. Edgar Thurston, of tlie 
Madras Museum ; i- and the latest conclusions of 
Science appear to be entirely favourable to the 
" parasite" theory. 
The fact that pearls may be arlifieially producerl 
by inserting small shot or grains of sand between 
the mantle and the shell of the animal has long 
been known. The (Chinese have been specially 
successful in prolucing pearls in this way; but 
the best of them are of inferior colour and bright- 
ness, and their value is comparatively insignilicant. 
Linnteus, who was aware of the possibility of 
producing pearls artilicially, suggested the col- 
lection of a number of mussels, piercing iioles 
in their shells with a line auger to produce a 
wound, and afterwards "parking" them for five 
or six years to give the pearls time to grow. The 
Swedish G- iveriuiii'ut consented to try the exneri* 
ment, and long did S ). Pearls were produced, 
but were of little value, and the enterprise was 
finally abandoned as unsuccessful. 
The distinction between fine pearls and these 
intrusive bodies coated with iiaf.re was r c^ntlv 
demonstrated in an important Paiier read bei'^ro 
the Academie des Sciences, Paris, by M Leon 
Dlgueb. He alleges that the bitter have iK.'y 
the iridescence of mother-of-pearl, and are 
in origin analogous to the deposits which increase 
the shell. The true i>earl, he contends, has no 
conneciion with the shell itself, but is a patho- 
logical caleificaiion or "stone," and seems to 
arise from para'^iles. It begins with a .small sac 
of hunnur, v/bich becomes gelatinous and 
* " Ksport on the Natural History of the Pearl 
Oyster, Trincomalee," 18.59. 
t " Pearl and Ohank Fisheries o£ the Gulf of 
Mannar." 1894 p, 18. 
calcifies in a series of concentric layer.s, while 
at its centre may be found a cavity holding orj/anic 
matter, the remains of the parasites which gave 
it birth. * 
"Pearl,'' says Saville-Kent, "is, unfortunately, 
one of the substances impermeable to the recently 
discovered Rcintgen rays ; otherwise the solution 
of this mystery . . . might be easily achieved. 
May be, "however, in the near future a new xx., 
XXX., or other occult luniinant will be evolved 
whijh shall possess the property of laying bare 
and naked the nuclei of pearls. t 
THE PEARL FISHERIES OF AUSTR.A.LIA. 
The pearl fisheries of Australia have of late 
years developed considerable proportions ; they are 
conducted in the Torres Straits, on the coast of 
Queensland, and on the northern coast of Western 
Australia. Here the large pearl oyster M. 
margaritifera is lished, primarily for the sake of 
its shell, which furnishes the mother-of-pearl 
of commerce. Pearl themselves, when discovered, 
are regarded as more or less of a chance pro- 
duct, and are frequently appropriated by the 
hired di\er and boats' crew— and this may be 
said to be commonly the custom in ail the 
pearl fisheries of the South Seas. The total value 
of the pearl-shell fishery of Queensland alone 
amounted in 189S to £109,401 sterling 
On the northern shores of Australia, in addition 
to the mother-of-pearl shell (from which almost 
all Southern pearls are derived), there occur two 
other species, viz. , M . imb7-icata, Rve. , and M. 
Jucafa, Gouhl, which produce pearls. The latter 
is identical with the pearl oyster of the Gulf of 
Mannar ; but is, curiously enough, regarded 
with disfavour in the Australian region, where 
it is known as the "bastard" shell,— probably 
because its shell is of liHle value as mother-of 
pearl, and also, perhaps, because it does not 
produce fine "Oriental" pearls in the Southern 
Seas. 
The pearling grounds of Australia are leased 
out to various companies and individuals by the 
Government. These leases are granted only to ap- 
proved persons, and are subject to certain im- 
portant conditions and stipulations. No shell 
below a certain standard of growth is allowed to 
be removed from the banks : and all shell shipped 
tor exportation must be submitted to the inspection 
of a Government official specially appointed to 
guard the industry. Pearls may only be purchased 
by licensed dealers, and the Government reserves to 
themselves the right to prohibit at any time the 
collecting of pearls and pearl-shell on any particular 
part of the coast. A constant guard is maintained 
over the banks, and certain areas are prescribed by 
the Inspectors when they have reason to apprehend 
any danger to the oysters from the results of over- 
fishing. 
In the Australian fisheries modern diving appa- 
ratus is largely employed, the same being periodi- 
cally inspected by Government in order to prevent 
the use of defective gear. Diving for pearls by 
native divers without diving dress seems likely to 
be discontinued in this region — especially as it is 
now found that, as a rule, the best pearl oysters 
flourish at depths beyond the reach of unprotected 
divers. 
On the whole, these fisheries appear to be conduc- 
ted upon a more up-to-date and advance<l method 
than elsewhere. Some interesting experiments in 
• "Comptes Kendus," cxxviii., 1899, p. 1589-91. 
t " The Naturalist in Anstraiia," p, 201. 
