89 
other beds with the larvee of the pearl-producing parasites. 
This is exactly the idea that has lately been revived by a 
French professor. 
Turning now to Kuropean shell-fish we find that our 
countryman Robert Garner in 1871 associated the produc- 
tion of pearls in our common English mussel (Mytilus 
edulis) with the presence of Distomid parasites. 
Professor Giard, in 1897, and other French biologists 
since have made similar observations in the case of Donax 
and other Lamellibranchs—Giard describing* the Distomid 
worm which he found as a species of Brachycoeliwm. 
We now come to quite recent years, during which 
there has been great activity. Prof. Raphael Dubois in 
1901 ascribed the production of pearls in mussels on the 
French coast to the presence of the larva of Distomum 
margaritarum. The next year (1902) Dr. H. L. Jamesont+ 
followed with a more detailed account of the relations 
between the pearls in Mytilus edulis and the Distomid 
larvee, which he identified as belonging to Leucithodendrium 
(Brachycoelium) somaterie—the same sub-genus as Giard 
had found some years previously. Jameson’s observations 
were made partly at Billiers (Morbihan), the same locality 
at which Dubois had also worked, and partly at our 
Lancashire Laboratory at Piel. Dubois published a 
further note} in January, 1903, in which he stated that 
Jameson had come to Billiers after his departure and had 
confirmed the discovery made previously, first by Garner 
and then by himself. But Jameson had really done more 
than that. He had shown that it is probable that the 
parasite causing the pearl formation in our common mussel 
(not however in the Ceylon Pearl Oyster) is the larva of 
* Comptes rendus, Soc. de Biol., 13th Nov., 1897, p. 956. 
+ Proc. Zool. Soc., Lond., 1902, p. 140. 
+ Comptes rendus, Acad. Sei., 19 Jan., 1903. 
