1903. J on the Pearl Fisheries of Ceylon. 283 



to the supply, and remove the disappointing fluctuations in the 

 fishery. 



There are in addition, however, various minor causes of failure 

 of the fisheries, some of which we were able to investigate. The 

 pearl oyster has many enemies, such as star-fishes, boring sponges 

 which destroy the shell, boring Molluscs which suck out the animal, 

 internal Protozoan and Vermean parasites and carnivorous fishes, all 

 of which cause some destruction and which may conspire on occasions 

 to ruin a bed and change the prospects of a fishery. But in connec- 

 tion with such zoological enemies, it is necessary to bear in mind 

 that from the fisheries point of view their influence is not wholly 

 evil, as some of them are closely associated with pearl production in 

 the oyster. One enemy (a Plectognathid fish) which doubtless 

 devours many of the oysters, at the same time receives and passes on 

 the parasite which 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. 



lu 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 trans- 

 planting when required the growing young from unsuitable ground 

 to known and reliable " paars." 



Those were the main considerations that impressed me during 

 our work on the banks, and therefore, the leading points in the 

 conclusions given in my preliminary report (July 1902) to the 

 Governor of Ceylon ran as follows : — 



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

 healthy. 



2. There is no evidence of any epidemic or of much disease of 

 any kind. 



3. A considerable 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 

 poj^ulation. 



4. Many of the larger oysters were rei)roducing 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 I'aars. On the Periya Paar the number 

 of these probably amounted to over a hundred thousand million. 



7. A very large number of these young oysters never arrive at 

 maturity. Tbere are several causes for this : — 



8. They have many 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. 



