706' 
THE TEOPICAL 
AGKICULTURISt. [April 1, 1904. 
a power of locomotion that would enable them 
to migrate to any great distance ; but our obser- 
vations have convinced as that they liave powers 
of freeing sheinselves from saud, of niovuig to a 
better siluation, of re-attachiiig themtelves when 
torn olT from their mooring, and of repairing injuiies 
to shell and mantle, with which tkey are not 
usually credited. All these matters have an im- 
portant bearing upon some of the recommendations 
that follow. SVe have also shown that transporta- 
tion of oysters, both old and young, even for con- 
siderable distances, such as trom the Gulf of Mannar 
to Galle, a matter of four or five day, at the hottest 
season of theyear.is comparatively easy, i^ ordinaiy 
precautions be taken to keep the water in the vessels 
as cool as possible and to prevent any decomposition. 
Transplanted specimens, moreover, liouiished in our 
hands ; both at Gaile and in the Gulf of Mannar 
(where some were moved from ihe Multuvaratu 
to the Cheval) the oysters improved in health 
and grew rapidly in size when moved to a new 
locality. We have given the details of growth for 
both old and young oysters- in picceding pages. 
These experiments also were undertaken because 
of their bearing upon that transplantation, from 
overcrowded and unreliable paars to more suitable 
ground, which we advocate. Some of our experi- 
ments give us a very clear indication, wliich how- 
ever we could also obtain by observation on the 
Pearl banks, of the kind of 
FOKEIGN OBJECTS BEST SUITED FOK YOUNG 
PEARL OYSTERS. 
to settle down upon. And this leads us to recognise 
the value of natural "culch" or suitable hard 
objects, such as coral fragments, shells, and 
Nullipores, upon the bottom, and the importance 
of increasing the available area by the artificial 
culching" of the more sandy parts. We must 
not try to be too precise in regard to the position, 
sizes, and outlines of the paars. Our work in the 
" Lady Havelock" showed us that some spots 
around and between them are more or less 
hard-bottomed, aud even in some cases bore 
oysters and are evidently capable of becoming 
paars. On the other hand, it is clear from the 
records of the inspections that many parts of the 
known paars may be temporarily, and possibly 
eome parts even permanently, unsuitable for the 
attachment or rearing of oysters. We may con- 
sider then the whole pearl bank plateau of the 
Gulf of Mannar as potentially "paar" ground, 
tome parts ofiit better suited for one purpose and 
some for another, some parts more constantly 
covered by the shifting sands, others more 
regularly bare and hard. It is this that renders 
possible the farming operations, such as "culching' 
and transplanting, which we refer to in our 
"Kecommendations." The history of the pearl 
fisheries in the past, especially during then ne-. 
teenth century, has shown that — 
let — A number of the smaller paars, which are 
hard patches of limited extent largely covered with 
living corals, are practically worthless from an 
economic point of view. 
2nd. — Some, such as the Periya Paar, might be 
HBed as most valuable soarces of snpply of yonng 
brood oysters for transplantation, bat cannot be 
relied npon to prodnce an adult stock suitable for 
Ashing. 
3rd.— Others af^ain, such aa the frrcat Cheval Paar 
with its various subdivisions, and the North and Sonth 
Modragams, the Periya Paar Kerrai, and the Muttn- 
varatu Paar are very valuable and reliable grounds, 
npon which moat of the eacceasfal fisb^riea of the past 
century have taken place. Others, such as Chllaw 
Dutch Modragam, Alantura, aud Karativn, are less, 
reliable, but may be valuable on occasions. 
It became clear to us duiing our work on the 
"Lady Havelock," when we began to understand 
why it is thfit the Periya Paar is unreliable and 
the Gheval Paar bo much more satisfactory, that 
the main hope of introducing constancy of result 
and a regular succession of fisheries must rest upon 
a system of transplanting young strikes or broods 
of oysters when they make their appearance npon 
useless or unreliable paats to wherever there is 
room for them at the time upon ground where ic is 
known they will have a better chance of living aud 
growing to maturity. This raises the whole ques- 
tion of the causes of death of the pearl oysier, the 
reasons of the intermittence in the history of the 
fisheries, and the conditions which render some 
paars more reliable than others. The following 
statement gives a summary of our results. 
I. — The most important agent in causing 
AVIDESPREAD DEATH OF PEARL OYSTERS 
both young and old — in the Gulf of Mannar is the 
shiftins; of sand due to the strong currents, to the 
south-west monsoon, and no doubt occasionally to 
exceptional storms. We obtained a good deal of 
evidence as to the manner in which the saud is 
carried about and piled up by the currents and is 
churned up in places by the strong south-west 
monsoon, and we made observations as to the effect 
of burying oysters of different sizes in various 
amounts of sand. The successive broods which 
have appeared and as regularly disappeared upon 
the Periya Paar during the last quarter century 
have, there can be no doubt, been overwhelmed by 
the bottom currents caused by the south-west 
monsoon upon the bank which faces the deep water 
of the Indian Ocean. 
II. — Next in importance come, we consider, the 
ravages of natural enemies, the most important 
of which are — 
(a) Voracious fishes, chiefly rays (Trygon uranak) 
and file fishes (Balistes mitis and B, stellatus). (i) 
BoriDg mollnsca, chiefly Sistrimi spectrum an Pinaxia 
coronata, along with species of Nassu Murex, Parmtra, 
and Turhinella. (c) The boring sponge (Clione 
indica). (d) Boring worms (Leucodore). (e) Star 
fishes, chiefly PmfaceJ'os a.tiA Luidea. (/') Smother- 
ing moUuaca. such aa Modiola barbata, the " Suran,"- 
which weaves nests and other entanglements aronnd 
masses of young oysters, and may, when present in 
quantity, cause serious mortality. 
In regard to the fishes mentioned under (a), it 
is necessary to bear in mind, however, that from 
the peail fisheries point of view their influence is 
not wholly evil, as their ravages are closely 
associated with pearl production in the oyster. 
The plectognathid fishes, specially, which doubt- 
less devour many of the oysters, at the same time 
receive and pass on the parasite which leads to 
the production of pearl in others. The loss of some 
individuals is in that case a toll that we very 
willingly pay, and no one could advocate the 
extermination of that particular enemy. 
III. — There are still three other causes of death 
that requiie mention and may on occasions be 
serious, perhaps disastrous, viz,: — 
(a) Overcrowding. — The older are sometimes 
buried in masses of younger ones. The young are 
often piled together in such profusion as to inter, 
fere with each other's nutrition aud growth. 
Thinning out must and does take place. If it 
were done artificially, all or nearly all might be 
preserved ; if we leave it to be effected naturally 
