( 3 ) 
IL— HISTORICAL SUMMARY. 
A considerable paft 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 1866, 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 
i820,i- observed the blue diatom Navicula fusiforinis, variety ostrearia — which he then 
called Vib?'io 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 Navicula 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,i| 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 Alga; (common Cyanophyceae) 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. XVIII., p. 221 f Journ. de Physique, tome XCI., p. 222. 
% Quait. Journ. Microsc. Sci., vol. XXVI., p. 71. § Revue Maritime el Coloniale, iSSo. 
II Voyage d'E.xploration sur le littoral de la France, &c. 
IT Rapport au Ministre de la Marine relatif a I'Ostreiculture, &c., Paris, 1876. 
** Milth, Zool. .Stai. Neapel. lSy6, p. 381. 
