110 CEYLON PEARL OYSTER REPORT. 



the results under a few main headings. It will be readily seen that these overlap in 

 places, that the groups are not all of the same value, and that it has not been 

 possible to keep the " Summary of Conclusions" and the " Recommendations" strictly 

 separated. 



A. SUMMARY OF CONCLUSIONS. 

 I. THE PEARL BANKS THE PHYSICAL SURROUNDINGS OF THE PEARL OYSTER. 



The pearl oyster, or rather "mussel" (Margaritifera vulgaris, SCHUM.) of the Ceylon 

 fisheries lives in very pure and clean sea-water in the Gulf of Manaar on certain 

 patches of hard ground known as "paars" (see charts and maps in Part I.). There 

 is no strict line of demarcation between the paars and the neighbouring sea-bottom. 

 We have evidence to show that the outlines, and the extent of the paars, may be 

 altered from time to time by the weather. What is a hard patch one season may be 

 covered by an overwash of sand in the next, and then again be swept clear by an 

 exceptional storm or current. These changes, although they may occasionally cause 

 damage to an oyster bed, are not wholly detrimental ; they sometimes uncover fresh 

 ground upon which young oysters may settle, and they cause us to recognise that 

 the whole of the wide shelf within the 10-fathom line in the northern part of the 

 Gulf of Manaar is potential paar-ground, and is susceptible of artificial improvement 

 for purposes of cultivation. 



The paars are, for the most part, at depths of 6 to 9 fathoms, and those that are 

 best known as fishing grounds lie at a considerable distance from land, the Cheval 

 Paar 9 to 14 miles, the Periya Paar Karai 12 miles, and the Modragams about 

 8 miles from the nearest coast. 



The Muttuvaratu Paar, at about 4 miles off Karativu Island, is the only one 

 where important fisheries have been held that is near the shore. In no cases have 

 the pearl oysters been found between tide-marks, or contiguous to the beach, in the 

 Gulf of Manaar, although it has been shown that they can live in such a position 

 in the sheltered waters of Trincomalee. For further details as to the positions, 

 depths, extent and other characters of the paars, see the sections on " Description 

 of the Pearl Banks " in Part I., and on the " History of the Principal Pearl Banks" 

 in Part II. of this Report. 



The hard bottom of the paars is to some extent formed of corals and shells, but to 

 a much larger extent by a modern rock now forming in situ. This has been called a 

 " calcrete " (see " Report on the Sea-bottoms," by Mr. LOMAS, in Part I., p. 147), as 

 it is composed of the sand and neighbouring organic remains cemented into a con- 

 tinuous hard mass by carbonate of lime. 



It has been shown in this Report that the cementing, although no doubt in part a 

 chemical process, is in places a biological result, since it is largely due to the growth 

 of living Nullipores and Polyzoa especially the latter (see fig. l). 



