GENERAL SUMMARY AND RECOMMENDATIONS. 113 



the Muttuvaratu Paar by breaking up the north or south current into local eddies. 

 Similarly the South-east Cheval and Modragam Paars are within the influence of the 

 outflow from Portugai Bay. 



There is a general drift of the water over the banks from south to north between 

 April and September, and from north to south during the height of the north-east 

 monsoon, with intermediate periods of calms and variable winds from February to 

 April, and usually again in November. But we are still in want of more definite 

 information (such as can only be obtained by some years of observation and experiment 

 with "drifters") in regard to the usual surface drift during the periods of variable 

 winds between the monsoons, before we can be certain of the source of " spat " supply 

 to particular banks, or of the destiny of larvae produced from our adult oysters. 

 " Drift-bottle " experiments, such as have been recently made for fisheries purposes in 

 several European seas, should be instituted in the Gulf of Manaar. It is only after such 

 work has been carried on systematically for two or three years at least that it will be 

 possible to determine the course taken by the larval pearl oysters between the time 

 of hatching and the deposition of spat, and again between the attachment to floating 

 Algae and the appearance of young oysters on a paar. These are details which it was 

 impossible for us to determine in the time at our disposal in 1.902, but which could 

 be readily settled by the Marine Biologist if he were given the necessary facilities. 

 Such information will obviously be of value whenever it becomes necessary to decide 

 upon the best section of a bed of oysters to be reserved as a breeding stock. 



II. FAUNA AND FLORA THE BIOLOGICAL SURROUNDINGS OF THE PEARL OYSTER. 



The Fauna and Flora of the Gulf of Manaar, comprising the whole assemblage 

 of plants and the other animals, large and small, which surround the pearl oyster, 

 have a profound effect upon the well-being of the stock upon the beds, and hence 

 upon the prosperity of the fisheries. We have taken every opportunity of investi- 

 gating this fauna and flora ; and the results of our collecting are reported upon in 

 detail by specialists, in the series of Supplementary Reports given in these volumes. 

 It will suffice to point out here, that the microscopic forms floating in the water and 

 captured by our fine silk tow-nets included (l) the pearl oyster itself in its youngest 

 free-swimming stages, (2) its food, not merely when young, but throughout life, and 

 (3) young stages of the parasitic worms which infest the oysters and some of which 

 induce pearl-formation ; and that the larger animals on the sea-bottom sponges, 

 corals, starfish, molluscs, crustaceans, and fishes are the all-important enemies or 

 fellow-competitors of the oyster (for food and attachment areas and growing room), 

 which may ruin a promising bed either by their direct aggressive action or indirectly , 

 in the struggle for existence. 



It is impossible, until a careful study has been made of each case, to say which 

 members of the fauna and flora of an oyster bed are of most importance to its 



