94 CEYLON PEARL OYSTER REPORT. 



6. Food and feeding, and the respiratory and nutritive currents of water. Varying 



" condition " of different oysters. 



7. Growth, increase of the shell and repair of injury. 



8. Parasites Sporozoa, Cestodes, Trematodes, Nematodes, &c, and Commensals: 



their effect upon the oyster. 



9. Other diseased and abnormal conditions of the oyster. 

 10. Pearl-production, both artificial and natural. 



Some of these inquiries were merely the continuation of observations and experi- 

 ments we had made during our work in the " Lady Havelock," others were under- 

 taken with the object of settling definitely doubts that had been expressed or 

 difficulties that had been raised in the Inspectors' reports and other previous writings, 

 such as Sir W. C. Twynam's " Report on the Ceylon Pearl Fisheries," Colombo, 1900 

 a most useful summary of many previous documents, illuminated by a personal 

 experience of nearly half a century. Our results, although no doubt they could be 

 added to by further work, are I believe conclusive so far as they go ; and 

 consequently must be recorded even when, as in some cases, they merely corroborate 

 or extend what was observed by Kelaart, Thomas, Holdsworth, Thurston or 

 others. 



The powers of locomotion we found to be unexpectedly great, especially in the case 

 of young oysters (see some instances we gave on p. 58) ; and the capability of 

 detachment and re-attachment, and of renewed byssus-formation, is considerable. 

 These are clearly points of great practical importance in connection with our recom- 

 mendations as to the thinning out and transplanting of young pearl oysters. Such 

 transplantation could only be successfully undertaken in the case of oysters able to 

 find suitable stations in their new environment and to re-attach themselves securely. 

 The effect of burying in sand throws light upon some of the catastrophes that have 

 affected promising beds of oysters in the past, and the knowledge will be useful in 

 leading us to remove the stock in dangerous positions from such risks in the future. 

 The sexes are separate, and, as our experiments show, remain the same from 

 season to season : each individual is permanently either male or female. The natural 

 emission of both ova and spermatozoa has taken place in our tanks at the Galle 

 Laboratory, and we have reared the young pearl-oyster from the egg to a shelled 

 larval stage similar to one obtained in the tow-nets. On all the other points we have 

 I believe made some additions to knowledge which will be discussed below in the 

 special articles. 



In October, 1902, Mr. Hornell carried out my suggestion of a further examination 

 of Trincomalee Harbour and Tamblegam Lake. He gave ten days to the work and 

 got satisfactory results which I have already noted (see p. 41). 



Early in November he joined Captain Legue in the inspection of the pearl banks 



