32 



CEYLON PEARL OYSTER REPORT. 



washing of these samples and the valuation of the pearls picked out. The results 

 showed that the South-west oysters were the richest in peai'ls, the North-west 

 following closely, with the Mid-west unmistakably much poorer in yield. 

 The following table will make clear the relative returns : 



" The weight of pearls per 1000 oysters was very high in the case of those from the 

 South-west, which fact may be correlated with the size of these oysters being 

 considerably greater than that of the other two lots. In regard to the quality of the 

 pearls, the North-west oysters, while yielding a less weight, contained a much greater 

 proportion of 'cyst pearls' of excellent quality than those from the South-west, 

 which owed their greater proportionate weight of pearls to a noteworthy abundance 

 of ' muscle pearls. ' 



"External characteristics give the most meagre indication of what the pearl yield 

 may be in regard to ' cyst pearls ' the abundance, or otherwise, is connected with 

 the factors which control the relative abundance of the pearl-inducing cestode and 

 those which conduce to its death during encystment in suitable localities within the 

 tissues problems as yet obscure. The fact, however, is to be noted that dissection 

 showed the oysters from the North-west Cheval to be more extensively infested with 

 cestode cysts than those from the other districts, while the valuation sample showed 

 that cyst-pearls were much more abundant in these oysters than in those from either 

 the Mid-west or South-west Cheval sections. With regard to muscle pearls the 

 general fact stands out, deduced from my experience of two fisheries, that the more 

 vigorous and well grown are the oysters the more abundant are the muscle pearls." 



Shell-pearls. 



" At the close of the inspection, when the valuation samples of oysters had been 

 washed, I seized the unique opportunity thus afforded to examine over 30,000 pairs 

 of separated valves of the pearl oyster. I did this chiefly to see if any considerable 

 proportion of shell -pearls were induced by the irritation caused by perforation of the 

 shell by boring parasites sponges, lamellibranch molluscs and annelids. The result 



