71 



example in November 1902 samples of the same generation of 3| to 3J years old 

 oysters were obtained from four different beds, with valuation results as follows : — 



ES. A. p. 



Periya Par Karai 13 4 per 1,000 



South-east Cheval 10 4 



Mid-east Cheval 18 3 „ 



North-east Cheval 23 2 „ 



[n March 1887, oysters of a similar age from the Moderagam Par gave a pearl 

 valuation vield of but Rs. 9-14-3 per 1,000, while otber individuals of identical 

 asje from the North-west Cheval in the same year were valued as low as Rs. 6-15-0 

 per 1,000. 



Another instance of wide variation in pearl yield occurred in the valuation of the 

 4 I to 4| years old oysters fished this year (1901) from the "Western Cheval. Three 

 lots varied as follows : — 



ES. A. P. 



Soath-west Cheval 36 per 1,000 



North-west Cheval 33 12 „ 



Mid-west Cheval 20 4 



"With such wide divergence in oyster value from closely adjoining areas we can 

 never be sure of the pearl yield from a particular bank till we solve the riddle of the 

 pearl Cestode's life-history and are enabled to artificially increase the proportion of 

 infected oysters — a matter for marine biological investigation. 



Meanwhile it is satisfactory to know that the oysters which the Tolayiram Par 

 rears are of fair quality and capable of giving a high pearl yield. 



I have had no opportunity to inspect a series of successive generations of oysters 

 from any other Indian Par. The individuals seen from the Devi, Cruxian, and other 

 inshore Pars appear much inferior to those from the Tolayiram Par. They are small 

 for their reputed age, stunted in growth, and much encrusted with sponges, corals 

 and polyzoa. In general appearance they approximate to those Ceylon oysters that 

 hail from rocky beds — from the Muttuvaratu Par and the Mid-west and North-west 

 Cheval. 



The Tolayiram Par is the bank by far best suited to rear healthy oysters in 

 quantity. Unfortunately some of the characters which render it so suitable for this, 

 expose the oysters to heavy risks from the depredations of fishes. The bare level 

 bottom, free from clefts and crannies and boulders, gives the rock-perch and trigger 

 fish ( VeUamin and Kilati) every facility to devour enormous quantities of oysters 

 during the first year of their existence. The bank swarmed with these fishes in May 

 last and the question of the possibility of the present young oyster population coming 

 to maturity depends largely on whether there be many more oysters present than can 

 be consumed by these fishes in nine months or a year. When about one year old 

 the shells become stout enough to resist the sharp teeth of these fishes and the survi- 

 vors have a fair chance of living the allotted span of oyster existence, if the bank 

 be not harried by a shoal of oyster-eating rays (Rhinoptera spp.). These fishes, the 

 principal enemies of the adult oyster, are often of large size, five feet or more across 

 the disc and with mouth armed with milling teeth of great crushing power. They 

 are able to feed only upon comparatively level ground and unfortunately the Tolayiram 

 Par is of this character. On the Ceylon side, I once walked over an oyster bed 

 ravaged at the most but a few days previously. The sight was one never to be 

 forgotten ; everywhere the flat rock surfaces, originally densely packed with oysters, as 

 evidenced by occasional clumps remaining, and by multitudes of torn byssal cables 

 adhering still to the denuded surfaces, were stripped in large part. Wide lanes had 

 been ploughed through, every oyster gone within the breadth of the lane. At frequent 

 intervals lay piles of broken shells, crushed flat as if passed through a mill. 



