INTRODUCTION. 5 



Many reasons, some fanciful, others with more or less basis of truth, have beeD 

 given from time to time for the recurring- failures of the fishery ; and several 

 investigations, such as that of Dr. Kelaart (who unfortunately died before his work 

 was completed) in 1857 to 1859, and that of Mr. Holdsworth in 1865 to 1869, have 

 been undertaken without much practical result so far. . 



In September, 1900, after a continued failure of the fishery for ten years, I was asked 

 by the Colonial Office (acting on the advice of the Council of the Royal Society and of 

 Professor Ray Lankester) to examine the records and report upon the matter, and 

 in the following spring I was invited by the Government to go to Ceylon at the end of 

 the year, with a scientific assistant, and undertake such investigation into the condition 

 of the pearl banks as might appear necessary. I arrived at Colombo in January, 1902, 

 and, as soon as a steamer could be obtained, proceeded to the Gulf of Manaar. 



In April it was necessary to return to my University duties in Liverpool, but I was 

 fortunate in having taken out with me as my assistant Mr. James Hornell, who, it 

 was arranged, would remain in Ceylon for at least a year longer in order to continue 

 the observations and experiments Ave had started and complete our work. This 

 programme has been carried out, and Mr. Hornell has kept me supplied with almost 

 weekly reports, and with specimens requiring detailed examination. 



The s.s. " Lady Havelock " was placed by the Ceylon Government at my disposal 

 for the work of examining into the biological conditions surrounding the pearl-oyster 

 banks ; and this enabled me on two successive cruises of three or four weeks each to 

 examine all the principal banks, and run lines of dredging and trawling and other 

 observations across, around, and between them, in order to ascertain the conditions 

 that determine an oyster " paar." Towards the end of my stay I took part in the 

 annual inspection of the pearl banks, by means of divers, along with the retiring 

 Inspector, Captain J. Donnan, C.M.G., and his successor, Captain Legge. During 

 that period we lived and worked on the native barque " Rangasameeporawee," and 

 had daily opportunity of studying the methods of the native divers and the results 

 they obtained. 



It is evident that there are two distinct questions that may be raised -the first as 

 to the abundance of the adult " oysters," and the second as to the number of pearls 

 in the oysters, and it was the first of these rather than the frequency of the pearls 

 that seemed to call for investigation, since the complaint has not been as to the 

 number of pearls per adult oyster, but as to the complete disappearance of the shell-fish. 



Most of the pearl-oyster banks or "paars" (meaning rock or any form of hard 

 bottom, in distinction to " manul," which indicates loose or soft sand) are in depths of 

 from 5 to 10 fathoms, and occupy the wide shallow area of nearly 50 miles in length, 

 and extending opposite Aripu to 20 miles in breadth, which lies to the south of 

 Adam's Bridge. On the western edge of this area there is a steep declivity, the sea 

 deepening within a few miles from under 10 to over 100 fathoms; while out in the 

 centre of the southern part of the Gulf of Manaar, to the west of the Chilaw pearl 



