168 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY, 



EECENT INVESTIGATIONS ON PEAELS IN 

 SHELLFISH. 



By W. A. Herdman. 



In last year's report I referred to the work done by 

 Dr. H. L. Jameson upon pearl-formation in the Common 

 Mussel at Piel. Since then Mr. Hornell and I have 

 published a preliminary notice* of our results obtained 

 with the Ceylon Pearl Oyster ; and more recently several 

 French investigators, Seurat, Giard, Dubois and Boutan 

 have written short notes dealing with the same important 

 matter. 



As is so often the case, the first statement of the 

 correct view was made long ago and afterwards forgotten 

 or contradicted, and the more modern work is largely a 

 resuscitation, extension and demonstration of an older 

 view. Filippi, in 1852, showed that the parasitic Trematode 

 worm Distomum was the cause of pearl-formation in the 

 freshwater mussel of rivers and lakes, and other naturalists 

 soon after extended the discovery to other pearl-producing 

 molluscs and to other worm parasites. To Dr. Kelaart 

 belongs the honour of having first connected the formation 

 of pearls in the Ceylon oyster with the presence of vermean 

 parasites. He and the Swiss Zoologist Humbert, who was 

 with him at a pearl fishery off Aripu, found various parasitic 

 worms infesting the viscera and other parts of the pearl 

 oyster, and they agreed that these worms played an 

 important part in the formation of pearls. Kelaart more- 

 over, in 1859, made the remarkable suggestion, in the case 

 of the Ceylon pearl oyster, that it might be possible to 

 increase the quantity of pearls by infecting the oysters in 



>;: Southport British Association Report, Sept., 1903; and Report 

 on Ceylon Pearl Fisheries, Part I., Royal Society, Nov., 1903. 



