138 SPOLTA ZEYLANICA. 



the Sambore river, the Uppu-aru, and the Palampat-aar the freshen- 

 ing of the water appears to have a direct and injurious effect upon 

 the health of the oysters. The greater portion of the Tamblegam 

 lake seems to be much more independent of the rainfall than the 

 localities named, and successfully withstood the last rainy season. 

 The following table, kindly prepared at my request by Mr. H. 0. 

 Barnard, F.R.A.S., F.R.Met.S., Superintendent of the Meteoro- 

 logical Branch, shows the frequency of the rainfall in the 

 Trincomalee District during the months October, 1907, to March, 



VI. — Placuniculture. 



It is only necessary to state here that the first steps have been 

 taken towards placing the Placuna beds of the Tamblegam lake 

 under conditions of culture. In October, 1907, a hmited number 

 (about 450) of oysters was transplanted by hand from the natural 

 beds to a reserved enclosure ^narked off by stakes in Nachchikkuda. 

 In March, 1908, these " plants" were found to be in good condition, 

 and to have achieved their maturation in a normal manner. 



There is a strong theoretical reason in favour of planting the 

 oysters close together in a confined space. The effect of a fishery 

 is necessarily to thin out the beds, so that the few surviving indi- 

 viduals become isolated and more or less widely separated. As the 

 sexes are distinct the chances of fertilization are correspondingly 

 reduced after a fishery, and transplantation may therefore be 

 supposed to^jcounteract the effects of depletion. 



In March, 1908, a further experiment was set on foot. Twelve 

 baskets of special construction were suspended from crossed poles 

 in mid- water and stocked with mature oysters. It is hoped that 

 some result will manifest itself before the end of the year. 



Finally, one of the most necessary precautions in cultural oper- 

 ations, namely, the surveillance of the protected areas, has not been 

 neglected. Three watchers have been appointed by tlie Assistant 

 Government Agent at Trincomalee to look after the beds until the 

 next fishery takes place. 



Samples of the Plankton (floating micro-organisms) were collected 

 and preserved in October and March, chiefly with the object of 

 overtaking the free-swimming embryos oi Placuna; so far; however, 

 without success in this respect. Observations on other animals 

 associated with Placuna have been made, but these do not at present 

 affect the practical issues. 



