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ORIGIN OF PEARLS 43
tion in those mussels was the parasite above noted; and in later papers1 he included such other forms as At ax ypsilophorus within
the list of parasitic agencies which might excite the pearl-forming
secretions, comparing their action to that of the formation of
plant-galls.
The discovery of the parasitic origin of pearls was extended to the pearl-oysters and to other parasites by Küchenmeister 2 in 1856, by Möbius3 in 1857, and by several other investigators. Prominent among these were E. F. Kelaart and his assistant Humbert, who, in 1859 4
disclosed the important relation which the presence of vermean
parasites bears to the origin of pearls in the Ceylon oysters. These
naturalists 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." Dr. Kelaart likewise found eggs from the
ovarium of the oyster coated with nacre and forming pearls, and also
suggested that the silicious internal skeletons of microscopic diatoms
might possibly permeate the mantle and become the nuclei of pearls.
Unfortunately, Dr. Kelaart's investigations were terminated by his
death a few months thereafter.
In 1871, Garner ascribed the occurrence of pearls in the common English mussel (Mytilus edulis) to the presence of distomid larvae.5 Giard,6
and other French zoologists, made similar discoveries in the case of
Donax and some other bivalves. In 1901, Raphael Dubois confirmed the
observations of Garner, associating the production of pearls in the
edible mussels on the French coasts with the presence of larvae of a
parasite, to which he gave the name of Distomum margari-tarum, and boldly announced : "La plus belle perle n'est donc, en définitive, que le brillant sarcophage d'un ver." 7
Prof.
H. L. Jameson, in 1902, disclosed the relation which exists between
pearls in English mussels (Mytilus) and the larvae of Distomum somateriœ.8 The
life history of this trematode, as revealed by Dr. Jameson, is
especially interesting from a biological standpoint, since it is
entertained by three hosts at different times : the first host is a
member of the duck family ; the second is the Tapes clam ( Tapes decussa-tus), or perhaps the common cockle (Cardium edule), which incloses
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1"Memorie
della Reale Academia delle Scienze di Torino," 1855, Vol. XV, pp.
331-358; 1857, Vol. XVI, pp. 419-442, and 1859, Vol. XVIII, pp. 201-232.
'Müller's "Archiv für Anatomie," 1856, pp. 269-281.
3 "Die echten Perlen," Hamburg, 1858. Dr. Möbius died in Berlin, on April 26, 1908. He was born at Eilenburg, in Saxony, in 1825.
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* "Report on the Natural History of the Pearl Oyster of Ceylon," Trincomali, 1859.
5 "Journal of the Linnean Society," Vol. XI, pp. 426-428.
' "Société de Biologie, Séance du 29 décembre, 1903."
* "Comptes Rendus de l'Académie des Sciences," Vol. 133, pp. 603-605, Oct. 14,1901.
8 "Proceedings of the Zoological Society of London," Vol. I, pp. 140-166.
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