760 
THE TROPICAL 
AGRICULTURIST. [May 2, 19C4. 
takings for 1903, the balance of the funds available 
being allotted, propovtionately, to the remaining offers 
received. 
(6) Any dispute aiiaing as to the interpretation or 
working of the foregoing, rule3 shall be referred to the 
tirbunal of Arbitration of the Bengal Chamber of 
Commerce to be determined in accordance with the 
rules for the time being of the tribunal. 
THE CEi'LON PEARL FISHERIES AND 
THEIR ADMINISTRATION.* 
A very remarkable feature of the Ceylon pearl 
fisheries has been their uncertainty and inter- 
mittent character. Thus only thirty six fisheries 
took place during the nineteenth century, or. put 
in another way, for just half a century the fishery 
banks lay barren. These blank years sometimes 
followed one another in dreary succession, as 
may be seen from the fact that for seventeen years 
— from 1837 to 1854 — and again for nine years — 
from 1864 to 1873— practically no fishing was done. 
THE FAT AKD LEAN SEASONS. 
For a decade before the investigation em- 
bodied in this report was begun the beds lay 
tenantless. Oecasional breaks of five years or less 
account for the remainder of these years of 
famine. But this apparently inexplicable state of 
affairs is by no means ofcmodern date ; for centuries 
these fat and lean seasons have been the despair 
of those interested in the collection of these gems. 
All kinds of theories, or rather speculations, have 
been promulgated, but the mystery remained, until 
now, as impenetrable as ever. Undoubtedly, then, 
the immense importance and value of these fisheries 
called for some effort on the part of the Government 
not only to attempt a solution, but also to find a 
remedy for these years of failure; To this end the 
Colonial Office, acting on the advice of Prof. E 
Ray Lankester, invited Prof. Herdman to examine 
the records on this subject and to report to them. 
As a result of this report Prof. Herdman was in- 
duced by the Government to make a persotal 
inspection of the pearl banks. Taking with him 
Mr Hornell as his scientific assistant, he accordingly 
set out for Ceylon, and instituted a thorough 
examination of the whole question, the results of 
^•hich are set out in part, in the volume before us. 
A COMPLETE SURVEY OF THE SEA BOTTOM. - 
Without doubt the task that lay before these 
investigators was no light one, and it is equally 
certain that it has been admirably fulfilled. As 
the pages of this volunce show, the expedition has 
not only been abundantly fruitful in scientific 
results, but it has achieved the purpose for which 
it was dispatched. A complete survey of the whole 
6ea bottom of the pearl fisheries area has now been 
■made, partly by sounding and dredging and partly 
by the aid of divers. In some cases even Mr Hornell 
himself descended in a European diving dress. By 
this survey a thorough knowledge has been gained, 
not only of the nature of the ground best suited 
for the growth of the pearl oyster, but also of the 
dangers by which this animal is beset. 
NUMEEOUS ENlMirS OF THE OYSTEE. 
Flourishing beds may be depleted by the ravages 
of boring sponges, boring molluscs, starfishes, inter- 
• " Report to the Government of Ceylon on the 
Pearl Oyster Fisheries of the Galf of Manr »>•." By 
WA Herdman, D Sc, F R S, &c. Part Pp. xii plus 
807. (London : Royal Society, 1903.) 
nal parasites, and fishes, thoueh the destruction 
wrought by these is generally slight compared with 
the wholesale destruction caused by shifting sands 
due to current?, or churned up by the sonth-west 
monsoon. By way of illustrating the vast scale 
of catastrophes of this kind, an instance— one of 
several— may be selected here. One bed examined 
in March, extending over an area of sixteen square 
miles, was covered with enormous quantities of 
young oysters ''so closely packed that the bank 
mast have held not less than about a hundred 
thousand million." Early in November of the 
same year this spot was revisited, when this vast 
host was found to have vanished, having been 
buried in the sand or swept down the deep declivity 
outside the bed. The loss which results from 
overcrowding is, on some beds, almost as whole- 
sale. 
NATURE TO BE ASSISTED. 
If, however, Prof. Herdman's suggestions are 
carried out, this enormous waste will in future 
be prevented by the simple expedient of trans- 
planting to sheltered spots affording suitable 
conditions for growth and infection. Natnrehas 
often to be assisted in the preparation of these 
spots by the process known as " culching," that 
is, scattering the floor of the bed with rock, loose 
coral, and so on, to afford the necessary anchorage 
for the byssus of the young oyster. What 
havoc may be caused by starfishes can be 
gathered from the fict that a bank examined in 
March, 1902, lodged a crop of oysters estimated 
at 5| millions : by March, 1903, they had nearly 
gone ! 
NO DANGER OF OViRFISHINO. 
Over-fishing is another source of danger, though 
in future, if Professor Herdman's plan of trans- 
planting is judiciously carried out, this need not be 
feared. In many places, it has been discovered, 
fishing may be carried on by dredging instead of 
by diving, though there are many places where the 
nature of the bottom will still compel the services 
of the native diver. 
THE FORMATION OF PEARLS. 
On the question of the formation of pearls this 
book contains much of great interest, and yet 
fuller details are promised in the next volume. Only 
in extremely rare cases did these investigators find 
that the nucleus of a pearl is formed by a grain of 
sand. Boring sponges and burrowing worms cause 
the formation of pearls or pearly excrescences on 
the inner surface of the shell by the irritation which 
they setup. Pearls of a peculiar kind are found in 
the muscular tissues, usually the levators of the 
foot. These also have no organic nuclei, but seem 
to start as minute calcareous concretions, and may 
be extraordinarily abundant. Thus, at the inser 
tion of one of the levator muscles 23 small pearls 
were detected with the naked eye, whilst under 
the microscope 170 more tiny spherules were found. 
But the best " orient " or " cyst" pearls are those 
which occur in the mantle " or in the thick white 
lateral part over the stomach and liver, or even, 
secondarily, free in a cavity of the body." Caused 
by the secretion of concentric layers of nacre 
around the dead body of a parasite— generally that 
of a platy-helminthean larva — these pearls attain 
their greatest size in oysters of from three and 
a half to five years of age 
HISTORY OF THE PARASITE. 
This parasite has an interesting history. 
Commencing life as a free swimming embryo, 
