224 Mr. A.W.E.O’Shaughnessy on Green Oysters. 
for which he proposed the name of Vibrio ostrearius. These 
creatures he described as gelatinous, linear in shape, pointed at 
the extremities, rounded in the middle, being also contractile in 
that part, and charged with a quantity of green fluid. He says 
that they inhabit the water of the tanks or “ parks” in which 
the oysters are preserved, in such immense abundance at certain 
periods of the year that they can only be compared to the 
grains of dust which rise in clouds and obscure the air in dusty 
weather. 
In a résumé of his observations on this subject which he con- 
tributed to the ‘Journal de Physique,’ tome xci. (1820) p. 222, 
he observes that the change of colour takes place only in the 
“parks” or reservoirs of salt water, where the oysters are kept 
on being brought from the sea. These “parks,” which are about 
4 feet in depth, 200 to 250 feet in length by about 50 feet in 
breadth, are capable of containing from 500,000 to 600,000 
oysters: such are those of Marennes, Oléron, Courseulles, Caen, 
Havre, Dieppe, Tréport, &e. At certain seasons of the year, 
particularly from April to June, and again in September, the 
water becomes, in some of these reservoirs, of a dark-green tint ; 
even the small stones at the bottom of the tanks are covered 
with small green points or excrescences. Then, says M. Gaillon, 
the oysters which are destined to assume the same colour are 
placed, with great care, one by one, and side by side, in order 
that none may rest upon any of the others, and the supply of 
fresh currents of water is suspended for a longer or shorter 
period, according to the required intensity of the green. 
M. Gaillon rejects the supposition that the change of colour 
is the result of disease, on the ground that, having compared 
the green oysters with those of the normal tint, he found all the 
organs quite as healthy in the former as in the latter. ‘ 
To the opinion which has often been entertained, that the 
green colour is due to the numerous minute particles of marine 
plants which either themselves form the food of the oyster or 
communicate their colour to the water absorbed by it, he objects 
that the plants which most commonly find their way into the 
reservoirs are the Ulva compressa and the Conferva littorals, 
which are known to turn yellow with age, and which, if mace- 
rated and left for several days in jars of salt or even fresh water, 
will not communicate the least tint of green to the fluid, whereas 
both the mouth and stomach of the oyster are totally unfitted 
for such food as Ulvze or Confervee. 
By the aid of the microscope, M. Gaillon discovered that the 
little green excrescences with which the stones at the bottom of 
the tank were constantly studded were nothing more than a 
heap of the tiny animaleules which filled the water in myriads, 
