236 POPULAR SCIENCE MONTHLY. 



in a sense, Dubois' statement that — 'La plus belle perle n'est done, en 

 definitive, que le brillant sarcophage d'un ver. '* 



To Dr. Kelaart (1859) belongs the honor of having first con- 

 nected the formation of pearls in the Ceylon oyster with the presence 

 of vermean parasites. It is true that Filippi seven years before (in ' 

 1852), showed that the Trematode Distoinum duplicatum was the 

 cause of pearl formation in the fresh-water mussel Anodonta, and 

 Kiichenmeister (1856), Moebius (1857) and others extended the 

 discovery to some of the larger pearl oysters, and to other para- 

 sites; but it is probable that Kelaart knew nothing of these papers 

 and that he made his discovery in regard to the Ceylon oyster quite 

 independently. He (and the Swiss zoologist, Humbert, who was with 

 him at a pearl fishery) found "in addition to the filaria and cercaria, 

 three other parasitical worms infesting the viscera and other parts of 

 the pearl oyster. We both agree that these worms play an important 

 part in the formation of pearls; and it may yet be found possible to 

 infect oysters in other beds with these worms, and thus increase the 

 quantity of these gems." 



Thurston, in 1894, confirmed Kelaart 's observation, finding in the 

 tissues, and also in the alimentary canal, of the Ceylon oyster, 'larvae 

 of some Platyhelminthian (flat-worm).' 



Garner (1871) associated the production of pearls both in the 

 pearl oysters and also in our common English mussel {Mytilus edulis) 

 with the presence of Distomid parasites; Ciard (1897) and other 

 French writers have made similar observations in the case of Donax 

 and other Lamellibranchs ; and Dubois (1901) has more recently 

 ascribed the production of pearls in mussels on the French coast, to 

 the presence of the larva of Distomum margaritarum. Jameson 

 (1902) then followed with a more detailed account of the relations 

 between the pearls in Mytilus and the Distomid larvae, which he identi- 

 fies as Distomum {Bracliyccelium) somaterice (Levinson). Jameson's 

 observations were made on mussels obtained partly at Billiers (Mor- 

 bihan), a locality at which Dubois had also worked, and partly at the 

 Lancashire Sea-Fisheries Marine Laboratory at Piel in the Barrow 

 Channel. Finally, Dubois has just published a further notef in which, 

 referring to the causation of pearls in Mytilus, he says (p. 178) : "En 

 somme ce que ce dernier [Garner] avait vu en Angleterre en 1871, je 

 I'ai retrouve en Bretagne en 1901. Quelques jours apres mon depart 

 de Billiers, M. Lyster Jameson, de Londres, est venu dans la meme 

 localite et a confirme le fait observe par Garner et par moi." But 

 Jameson has done rather more than that. He has shown that it is prob- 



* Comptes Rendus, October 14, 1901. 



I Comptes Rendus Acad. d. Sci., January 19, 1903. 



