30 



CEYLON PEARL OYSTER REPORT. 



oysters at Trincomalee ; the fishes that are, in all probability, the hosts of the parasite 

 in its more advanced stages abound at various points. It is the molluscan host and 

 not the parasite that stands in need of artificial aid in Ceylon. If we can increase 

 the number of beds, and can prevent catastrophes from devastating the oyster 

 populations, so that the divers can collect them annually in their tens of millions, we 

 need not fear any scarcity of pearls. 



As Boutan, who thinks favourably of artificial methods, points out* : " Mais il ne 

 faut pas oublier que l'infection d'un animal par un parasite ne favorise pas precisement 

 le developpement normal du sujet infeste." He advocates as an alternative method 

 experimental trepanning of the shell, but that or any other mode of individual 

 treatment is clearly impracticable in dealing with the millions of the Ceylon pearl 

 banks. Our own opinion is that, although all pearl-production is a departure from 

 the normal, the pearl-inducing parasites are not sufficiently abundant to affect 

 seriously the health of the oyster ; and that, to reverse the popular saying, if we 

 attend to the prosperity of the bed as a whole, the individual oysters may be left to 

 take care of themselves, both in regard to health and pearl-production. 



DISTRIBUTION OF PEARLS. 



Figs. 5A and 5B, on p. 27 show the usual distribution of cyst and muscle pearls 

 respectively in the Ceylon pearl oyster. The following table will show the numerical 

 proportion between the two kinds in various parts of the body. It is the summary of 

 a number of observations made by us in 1902 and 1903 : 



' Arch, de Zool. exper.,' 1904, p. 89. 



