THE TROPlCAlj 
AGEICULTUKIST. [July 1, 1903. 
fathoms is situated the largest of the " Paars," 
celebrated PeriyaPaar,\vhicli has frequently fif!;ured 
in the inspectors' repoits, has often given rise to 
hopes of great fisheries, and has as often caused 
deep disappniiitnient to successive Government 
officials, Tlie Periya Paar runs for aV.ouc 11 nauti- 
cal miles north and south, and varies from one to 
two miles in breadth, and tliia— for a paar— large 
extent of ground becomes periodically covered with 
young oysters, which, however, almost invariably 
disappear before the next inspection. This 
paar has been called by the natives the " mother- 
paar," under the impiession that the young oysters 
that corne and go in fabulous numbers migrate 
or are carried inwards and supply the inshore 
paais witli their populations. During a careful 
investigation of the Periya Paar and its surround- 
ings, we satisfied ourselves that there is no basis 
of fact for this belief ; and it became clear to us 
that the successive broods of young oysters on the 
Periya Paar, amounting probably within the last 
quarter century alone to many millions of millions 
of oysters, which if they had been saved would 
have constituted I normous fisheries, have all been 
overwhelmed by natural causes, due mainly to the 
configuration of the ground and its exposure to 
- the south-west monsoon, 
A study of the history of the Periya Paar for the 
last twenty-four years shows that since 1880 the 
bank has been naturally restocked with young 
oysters at least eleven times without yielding a 
fishery. 
The 10-fathom Une skirts the western edge of 
the paar, and the lOO-fathoni line is not far out- 
side it. An examination of the great slope outside 
is Sufficient to sliow that the south-west monsoon 
running up towards the Bay of Bengal for six 
months in the year must batter with full force on 
the exposed seaward edge of the bank and cause 
great disturbance of the bottom. We made a 
careful survey of the Periya Paar in March, 1902, 
anj found it covered with young oysters a few 
H»onths old. In luy preliniinary report I esti- 
i^ated these young oysters at not less than 
A HUNDRED THOUSAND MILLIONS, 
and stated my belief that these were 
doomed to destruction, and ought to be 
removed at the earliest opportunity to a 
safer locality further inshore. Mr, Hornell was 
authorised to cany out this recommendation, and 
went to the Periya Paar early in November with 
boats and appliances suitable for the work, but 
found he had arrived too late. The south-west 
monsoon had intervened, the bed had apparently 
been swept clean, and the enormous population of 
young oysters, which we had seen in March, and 
which might have been used to stock many of 
the smaller inshore paars, was now in all pro- 
bability either buried in sand- or carried down the 
steep declivity into the deep water outside. This 
experience, taken along with what we know of 
the past history of the bank as revealed by the 
inspectors' reports, shows that whenever young 
oysters are found on the Periya Paar, they ought, 
without delay, to be dredged up in bulk and 
transplanted to suitable ground in the Cheval dis- 
trjPt-Lthe region of the most trustworthy paars. 
From this example of tlie Periya Paar it is dear 
that in considering the vicissitudes of the i)earl 
oyster banks we have to deal with great natural 
causes which cannot be removed, but which may 
to some extent be avoided, .and that consequently 
is necessary to introduce large measures of 
cultivation and regulation in order to increase tlie 
adult po[)ulation on the grounds, and give greater 
constancy to the su))ply. 
There are ;in addition, however, various minor 
causes of failure of the fisheries, some of which 
we were able to investigate. The pear! oyster has 
many enemies, such as star fishes, boring sponges 
which destroy the shell, boring Molluscs which 
suck out the animyl, internal Protozoan and Ver- 
mean parasites and carnivorous fishes all of which 
cause some destruction, and which may conspire 
on occasions to ruin a bed and change the pros- 
pects of a h-hery. But in connection with such 
zoological enemies, it is necessary to bear in mind 
that from the fisheries point of view their iniiuence 
is not wholly evil as sorne of them are closely 
associated with pearl production in the oyster, 
One enemy (a Plectoguathid lish) which doubtless 
devours many of the oysters, at the same time 
receives and passes on the parasite v.hich leads to 
the production of pearls in others. The loss of 
some individuals is in that case a toll that we 
very willingly pay, and no one would advocate the 
extermination of that particular enemy. 
In fact the oyster can probably cope well enough 
with its animate environment if not too recklessly 
decimated at the fisheries, and if man will only 
compensate to some extent for the damage he does 
by giving some attention to the breeding stock and 
" spat,'' and by transplanting when required the 
growing young from unsuitable giound to known 
and trustworthy " paars. " 
Those were the main considerations that im- 
pressed me during our work cn the bunks, and 
were, therefore, die leading points dealt with in 
the conclusions given in my preliminary repoit 
(July, 1902), which ended as follows :—" To the 
biologist two dangers are, however, evident, and, 
paradoxical as it may seem, these are overcrowd- 
ing and overfishing. 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 failuie 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 problenis 
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 
REGULATION OF THE FISHERIES," 
In connection with cultivation and trans- 
plantation, there are various points in structure, 
reproduction, life-history, growth and habits of the 
oyster which we had to deal with, and some of which 
we \> ereable to determine on the banks, while others 
have been the subject of Mr Hornell's work since, 
in the little marine laboratory we established at 
Galle. [Discussed and illustrated by lantern slides.] 
Turning now from the health of the oyster popu- 
lation on the "paars" to the subject of pearl 
formation, which is evidently an unhealthy ab- 
normal process, we find that in the Ceylon oyster 
there are several distinct causes that lead to the 
production of pearls. Some pearls or pearly excre- 
scences on the interior of the shell are due to tlie 
irri'alion caused by boring sponges and but rowing 
worms. Minute grains of sand and other foreign 
bodies gaining access to the body inside the shell, 
which are popularly supposed to form the nuclei ot 
