TEE PEARL FISHERIES OF CEYLON. 233 



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 the 

 bulk and transplanted to suitable ground in the Cheval district — the 

 region where the most reliable paars are placed. 



From this example of the Periya Paar it is clear that in consider- 

 ing the vicissitudes of the pearl oyster banks, we have to deal with 

 great natural causes which can not be removed, but which may to 

 some extent be avoided, and that consequently, it is necessary to 

 introduce large measures of cultivation and regulation in order to 

 increase the adult population on the grounds, give greater constancy 

 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. 



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 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 con- 

 clusions 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. 



