132 SPOLTA ZEYLANICA. 



months of November, December, January, and February, 

 from the Challai, Alanturai, Dutch Moderagam, and Karativu 

 Paars, have been carefully examined by Captain Sewell, B.A., 

 I. M.S., Surgeon Naturalist to the Marine Survey of India and 

 Professor of Biology in the Medical College, Calcutta. The 

 pearl banks have not been entirely barren during the whole of 

 the time over which the collections were made. Yet no trace 

 of oyster larvse has been found in these plankton collections. 

 A few such larvse have been noted in two plankton catches 

 from Marichchukkaddi Bay. Such larvse have undoubtedly 

 come from the inshore bed of oysters on the Kondatchi Paar. 

 The oysters on this and other inshore beds spawn irregularly 

 {Ceylon Marine Biological Reports, Part V., page 202). The 

 Kondatchi Paar lies about eight miles north of Marichchukaddi 

 Bay, and as the wind was north during the time when the 

 plankton was collected (north-east monsoon) the occurrence of 

 a few oyster larvse m the catches from Marichchukkaddi Bay 

 is readily understood. It is possible that such a circumstance 

 may account for the phenomenon observed by Hornell. 



Dr. Pearson is only partly correct in stating that we 

 established the presence of a current during the north-east 

 monsoon, which, sweeping the Ceylon banks, was capable of 

 carrjdng pearl oyster larvse from the Ceylon to the Indian 

 side. We stated that during the north-east monsoon an 

 oceanic current ran up the west coast of Ceylon as far as 

 Tallaivillu Point, and from thence took a westerly course. 

 North of this point the surface currents (drifts) vary even 

 during the day with the direction of the wind by which they 

 are controlled, and to which they entirely owe their existence 

 [Ceylon Marine Biological Beports, Part VI., page 232). 



It frequently happens that bottles liberated on the pearl 

 banks during the north-east monsoon are blown south and 

 become involved in the current running west. Our results 

 showed that 16*76 per cent, of bottles liberated on the pearl 

 banks during this monsoon were recovered from Southern 

 India. In other words, 83*24 per cent, of bottles were lost. 

 Spat, if present, would take a similar course. The great 

 bulk of it would be lost. It will be noted, however, that even 

 if spat is liberated during the north-east monsoon the chances 



