SEA-FISHERIES LABORATORY. 169 



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 European 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 Brachycoelium. 

 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. Jameson! 

 followed with a more detailed account of the relations 

 between the pearls in Mytilus edulis and the Distomid 

 larvae, which he identified as belonging to Leucithodendrium 

 (Brachycoelium) somaterus — 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 



* Coruptes rendus, Soc. de Biol., 13th Nov., 1897, p. 956. 



f Proc. Zool. Soc, Lond., 1902, p. 140. 



I Goruptes rendus, Acad. Sci., 19 Jan., 1903. 



