280 Professor W. A. Eerdman [INIarch 27, 



1902, and as soon as a steamer could be obtained proceeded to the 

 pearl banks. 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 was to remain in Ceylon 

 for at least a year longer, in order to carry out the observations and 

 experiments we had arranged, and complete our work. This pro- 

 gramme has been carried out, and Mr. Hornell has kept me supplied 

 with weekly reports and with specimens requiring detailed examina- 

 tion. 



The PS. Lady Havelock was placed by the Ceylon Government 

 at my disposal for the work of examining into the biological condi- 

 tions 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 bed. 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 Bangasamee- 

 poraicee, 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 fiequency 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 disappear- 

 ance of the shell-fish. I was indebted to Captain Donnan for much 

 kind help during the inspection, when he took pains to let me see as 

 thoroughly and satisfactorily as possible the various banks, the 

 different kinds and ages of oysters, and the conditions under which 

 these and their enemies exist. I wish also to record my entire satis- 

 faction with the work done by Mr. Hornell, both while I was with 

 him and also since. It would have been quite impossible for me to 

 have got through the work I did in the very limited time had it not 

 been for Mr. Hornell's skilled assistance. 



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 60 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 Banks, depths of 

 between one and two thousand fathoms are reached. On our two 

 cruises in the Lady Havelock we made p ^.areful examination of the 



