PEARL PRODUCTION. 7 



the presence of vermean parasites. He and the Swiss zoologist, A. Humbert, who 

 was with him at a pearl fishery off Aripu in 1857, found various parasitic worms 

 infesting the viscera anil other parts of the pearl oyster, and they agreed that these 

 worms played an important part in the formation of pearls. Kelaart moreover, 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 other 

 beds with the larvae of the pearl-producing parasites. This is exactly the idea that 

 has lately been revived by Dubois in Fiance. 



Observations on Mytilus Pearls. 



Turning now to European shell-fish, we find that our countryman, Robert Garner, 

 in 1863 and again in 1871* associated the production of pearls in our common 

 English mussel (Mytilus edulis), as well as in Anodon, 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 lie found as a species of Brachyccelium which he has 

 identified since with Distomum constrictum, Mehlis. Lon Diguet, in 1899, 

 described the pearl-sac which secretes concentric layers of the nacreous deposit 

 around the remains of parasites. We now come to quite recent years, during 

 which there has been great activity. Professor Raphael Dubois, in 1901, ascribed 

 the production of pearls in mussels on the French coast to the presence of the larva 

 of Distomum marga/ritarum. 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 Distomum {Brachyccelium) 

 somaterice the same sub-genus as Giard had found some years previously in other 

 Lamellibranchs. Jameson's observations were made partly at Billiers (Morbihan), 

 the same locality at which Dubois had also worked, and partly at the Lancashire 

 Sea Fisheries Laboratory at Piel, in the Barrow Channel. 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 much more than that. 

 He had shown that it is probable that the parasite causing the pearl formation in our 



* 'British Association Report' for 180:3, p. 114; and 'Journ. Linnean Soc, Zool.,' vol. xi., p. 426. 



t 'Comptes Eendus Soc. Biol.,' November 13, 1897, p. 956. 



t 'Proc. Zool. Soe. Lond.,' 1902, p. 140. 



Giard states (' Feuille des Jcunes Naturalistes,' January 1, 1904) that this species is the Distomum 

 amstiictamoi MEHLIS, but there eems some reason to believe that Jameson had more than one species 

 under observation. 



|| 'Comptes Rendus Acad Sci.,' January 19, 1903. 



