( 3 ) 



II. — HISTORICAL SUMMARY. 



A considerable part of our work has dealt with "greenness" in oysters of different 

 kinds — a subject on which many contradictory statements have been made, and which has 

 a curiously involved history. 



In 1 866, Mr. A. W. E. O'Shaughnessy* gave an excellent account of our knowledge 

 of the "greening" of oysters up to that date. He showed how M. Benjamin Gaillon, in 

 1820,-f- observed the blue diatom Navicula fusiformis, variety ostrearia — which he then 

 called Vibrio ostrearius — in the " Claires " of the Oyster Merchants at Marennes, &c, in 

 France, and attributed to it the dark bluish green tint of the gills, palps, intestine, and 

 liver of the cultivated oyster. He also discussed the observations of Valenciennes, 

 Dumas, Bizio, Buckland, and others ; and cited some historical cases of poisoning 

 supposed to be due to the presence of copper in large quantities in green oysters. As 

 these earlier observations are discussed also by Professor Ray Lankester in his important 

 paper in 1885, J they need not be further alluded to here. But we must add to 

 Lankester's record by referring to Puysegur,§ who, in 1880, gave an account of certain 

 experiments, in which he stated that he had succeeded in turning oysters green in some 

 few hours by feeding them upon the diatom Aavicula ostrearia. It has also been shown 

 experimentally by Bornet, Decaisne, and others, that white oysters can be greened 

 rapidly by keeping them in clean soup plates and feeding them with water containing 

 the Navicula. These interesting experiments were carried out at Le Croisic, in Brittany, 

 and were afterwards repeated in Paris, and the result seems entirely opposed to the old 

 suggestion, due originally to Coste,j| in 1861, that iron salts in the soil at the bottom 

 of the " Claire " are the cause of the greening, which suggestion was alluded to again 

 more than twenty years ago by Bouchon-Brandely,^! and has quite recently been revived 

 by Carazzi** at Spezia. Moreover, Bornet and Ad. Chatin have shown that in the parks 

 at Sable d'Olonne the greening may be suddenly manifested where the oysters had 

 previously remained white, under circumstances where the microscopic fauna and flora 

 of the water may well have changed, but where the floor of the park has undoubtedly 

 remained the same. Finally, Mr. E. Newman, manager of the Colne River Oyster 

 Beds, has shown us that when the Algse (common Cyanophyces) in his ponds get 

 into a certain condition, he can convert the ordinary colourless Colchester " native " into 

 a green-gilled oyster in 24 hours. 



* Ann. and Mag. Nat. Hist., vol. XVJII., p. 221 t Journ. de Physique, tome XCI., p. 222. 



X Quart. Journ. Microsc. Sci., vol. XXVI., p. 71. § Revue Maritime et Coloniale, tSSo. 



II Voyage d'Exploration sur le littoral de la France, &c. 



1T Rapport au Ministre de la Marine relatif u l'Ostreiculture, &c., Paris, 1876. 



" Mitth. Zool. Stat. Neapel. 1896, p. 381. 



