CEYLON PEARL BANKS. 2l9 



anew when next the opportunity presents itself. The question of 

 the currents is one of more than academic interest, and it is not 

 improbable that \^'hen our knowledge of both the currents of the 

 Gulf of Mannar and the life-history of the pearl oyster is more com- 

 plete than at present, the way will be cleared for the elucidation of 

 some of the problems which have hitherto baffled inquiry. It may 

 be claimed that the knowledge gained by these current investiga- 

 tions has no practical value. It is true that man cannot attempt to 

 control the numerous factors which together effect a spatfall. A 

 lull in the monsoon, a slackening of the current, or any one of a 

 hundred other causes may be sufficient to prevent the larvae reaching 

 favourable ground. But there is another aspect of the current 

 investigations which would appear to hold out some promise, and it 

 is an aspect which hitherto does not appear to have been considered 

 very seriously. 



In view of the proposals which have been put forward from time 

 to time to establish breeding reserves, it is necessary to make an 

 intensive investigation of the comparatively small area of the banks 

 in order to determine the nature of the currents and surface drift. 

 To establish breeding reserves will be futile, unless we know that 

 spawning will be followed by a spatfall on the banks themselves. 

 The only object of the breeding reserves is to maintain the produc- 

 tivity of the banks, hence this object fails if OAving to cm-rents or 

 surface drift the pelagic larvae are carried off the banks. 



If drift-bottle experiments show that the drift over the banks 

 during, say, the July spawning maximum is very slight, then there 

 would be reason to hope that any larvae liberated on the banks 

 would not be carried away, and this would prove of great value 

 on subsequent efforts to maintain the productivity of the beds. 



1 have already hinted that in the December spawning maximum 

 spawn from the Cejdon pearl banks may be carried over to Tuticorin, 

 but this would not be the case in the July maximum. 



Altogether the question of breeding reserves raises many points of 

 great interest, and before we can be convinced of success in this 

 matter, we must first of all know more about spawning periods of the 

 pearl oyster, the duration of the larvae stage, and the disposition of 

 the tides, currents, and surface drift on the banks. 



Summary of the Position. 



The present position of the question appears to show that so long 

 as the banks are barren the part played by man must be a passive 

 one. He is entirely dependent upon Nature for the re-population of 

 the banks, and so far as one can see nothing can be done to hasten 

 a spatfall in such circumstances. Dr. Jameson's suggested importa- 

 tion of a " few thousands of young spat " presents many difficulties. 

 For the experiment to be of any value many milHons of young spat 

 would have to be imported. The cost and trouble of transport from 



2 G 6(7)12 



