RECENT INVESTIGATIONS ON PEARLS IN 
SHELLFISH. 
By W. A. Herpman. 
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 unportant 
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 
molluses 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. Melaart more- 
over, in 1859, made the remarkable suggestion, in the case 
of the Ceylon pearl oyster, that it might be possible to 
inerease 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, Noy., 1903. 
