LINNEAN SOCIETY OF LONDON'. 2$ 



According to an interesting note by Prof. Giard *, the discovery 

 of Cestode larvae as nuclei of pearls, which we had made upon the 

 Ceylon Pearl-Oyster in 1902, was shortly afterwards corroborated 

 by Dr. L. G. Seurat, working independently in his Laboratory at 

 Eikitea in the island of Mangareva (Gambler Archipelago). The 

 oyster on which Seurat worked was Mavgaritifera margaritifera, 

 var. cumingi, Eeeve, and tlie Cestode parasite found is, according 

 to Giard, an Acrobothrium ( = Cifathocephahis) or some allied form. 

 It is possible that some of our Ceylon Pearl-Oyster parasites may 

 also belong to the genus C'ljathocepTialus, although most of them 

 are certainly Tetrarhynchids. 



Giard in a further note in the same Journal (p. 1225) discusses 

 the statements that have been made in regard to " margarose 

 artificielle," and evidently considers that Dubois's claim to have 

 established the artificial production of pearls is not yet justified 

 by the facts. Last of all Boutan t shows that " fine pearls " do 

 not really differ from " nacre-pearls '' since both are secreted from 

 open or closed epithelial sacs derived from the epidermis ; and 

 Giard very properly replies a few days later t that this fact is 

 quite in accord with general principles, and was previously known. 

 M. Boutan in a letter (20th Jan. 190-1) states that he is on the 

 point of departure for the East in order to investigiite the matter 

 further. But so far as I am aware, he has as yet made no further 

 contribution to the subject. 



In what I told you of Linnaeus and pearls last year, the pearl- 

 forming mollusc was a freshwater mussel of the genus Unio. In 

 the greater part of what I have told you now of the recent in- 

 vestigations on the coasts of France and England, the molluscs in 

 question belong to the genus Mijtilus. But the pearl-formation in 

 which I personally have taken most interest, and which is of the 

 greatest importance to the pearl-merchant, is the Ceylon Pearl- 

 Oyster belonging to the genus Margaritifera, — and to that I now 

 pass. 



I desire to pay passing tribute to the work of a pioneer. It was 

 Dr. Kelaart who, in the Gulf of Mauaar, half a century ago, first 

 connected pearl-formation in a true pearl-oyster with the presence 

 of Termean parasites. In his ' Introductory Eeport on the 

 Xatural History of the Pearl-Oyster in Ceylon' (1857), after 

 describing the secretion of nacre by the mantle, he said : — " It 

 AviU be thus clearly understood that when a gi'ain of sand or the 

 larva of an insect is introduced between the mantle and shell, it 

 will become covered over with the pearly secretion, which, always 

 going on, is augmented at the part where the foreign matter lies. 

 This phenomenon I have detected with the aid of the microscope 

 in its very earliest stage."' The probability is that by " larva of 



* Comptes Kendus, Soc. Biol. Paris, 6 Ifov. 1903, Iv. p. 1222. 

 t Comptes Rendus Acad. Sci. 14 Dec. 1903, p. 1073 ; and also Arch. Zool. 

 Exp.'1904. 



X Comptes Rendus, Soc. Biol. Paris, 19 Dec. 1903, p. 1618. 



