WINDOW-PANE OYSTER, 225 



predaceous fish ; and to the iUicit diving and poaching practised 

 by the Kinniyai villagers. 



The first of these dangers is a serious one. It is unfortunate that 

 the part of the oj^ster bed which is richest in oysters Ues off the 

 mouths of the Sembian-aar and the Polokarai-aru, and hence is most 

 affected by inrushes of fresh Avater. Transplantation would appear 

 to be the only remedy for this very serious danger. It is never- 

 theless a fact that the oysters are more abundant in the southern 

 half of the main bed, which is close to the rivers, than in the northern 

 half, which is more remote from the mouths of the rivers. One 

 reason of this is undoubtedly because the soft ooze upon which the 

 oysters flovunsh best is carried down by the rivers, and is therefore 

 more abundant opposite the mouth of the rivers. It is also certain 

 than Placima flourishes best in water of low density. The actual 

 relation between the distribution of the oyster and the salinitj^ of the 

 water has not yet been determined. It is proposed to carry out this 

 work for the first time in the January inspection. 



If the transplantation experiments show that the oysters thrive 

 best on the soft mud off the mouths of the rivers, as is highly 

 probable, then we are presented with the paradox of the rivers 

 proving both beneficial and harmful. To determine the resultant 

 of these opposing factors will offer a nice problem to the marine 

 biologist. 



The ravages of predaceous fish are indisputable, audit is probable, 

 as pointed out by Dr. Wille}^, that the young oysters are particular^ 

 in danger from this source. I have recently had this fact brought 

 home to me very plainh\ In January of this year an enclosure was 

 made in Nachchikkuda and oysters were transplanted from area H. 

 In May these had all disappeared, and broken shells gave unmis- 

 takable signs of fish having been the depredators. The enclosure 

 was surrounded by wire netting supported by strong stakes and 

 railway rails, and the fish had buried under the netting and thus 

 gained entrance. In June the enclosure was further strengthened 

 by the addition of numerous upright stakes about 3 inches 

 apart, and the enclosure was again stocked. In the September 

 examination nothing but broken shells were found in the enclosure , 

 and the nature of the bites showed that a Tetrodon had probably 

 been the culprit. 



These experiments, although the 5^ failed in their main point, 

 proved indisputably how important a factor predatory fish are in the 

 bionomics of the window-pane oyster. 



The question of poaching is one which demands serious considera- 

 tion. The Moormen of the Kinniyai district are bom thieves and 

 marauders. They have a not unnatural desire to investigate the 

 wealth of oysters which lies so conveniently near. The presence of 

 the two watchers but feebly reminds the Kinniyai villager of those 

 remote and shadowy things — law and order— and perhaps add just 



