766 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [14] 
small animal (Vibrio ostrearius), and also to a disease of the oyster, a 
sort of jaundice or affection of the liver; but to-day it appears certain 
that this coloration is due solely to the peculiar nature of the soil form-. 
ing the bottom of the claires, and that every park having as a basea soil 
composed of a blue or a rich ferruginous clay will give to oysters placed 
in it this esteemed color; but this character will no, longer be of any 
importance when colorless oysters raised in parks whh the same care as 
those in the claires at Marennes shall present the same qualities. Upon 
those coasts where favorable circumstances permit their multiplication, 
oysters form beds or banks often several hectares (a hectare is 2.41 acres) 
in extent. These banks are formed by the aggregation of oysters of 
different ages and sizes, whose shells become firmly attached or soldered 
to the stones or rocks covering the bottom or to the shells of neighbor- 
ing oysters. If it were not for the destructiveness of oyster-fishing, 
these banks would go on increasing insize and depth, without limitation, 
and also, as a natural result, in value, by the annual accumulation of 
new germs; an accumulation singularly favored by great numbers of 
vacant places over the bottom of the ocean.* The oysters which are 
most esteemed in Europe come from England, while the best of the French 
oysters are found upon the coasts of Brittany and Normandy. Those 
most commonly eaten at Paris come from the north, from Cancale, Dieppe, 
Eitretat, Dunkerque, &c. The southern and central portions of France 
are supplied from Bordeaux and Rochelle, and from the few rare banks 
of the west coast which are not yet exhausted. 
The principal parks are those of Marennes, Saint-Waast, Courceul, 
Etretat, Fécamp, Dieppe, Tréport, and Dunkerque. The fishing is done 
by means of a dredge, which is dragged over the bottom ofthe sea. This 
dredge scrapes over the soil and gathers up into a bag of leather or twine, 
which is attached behind it, everything that lies in its course. When 
the dredge net is felt to be full the dredge is drawn on board of the 
boat and its contents emptied and sorted, those oysters only being re- 
tained which are of the size established by law, the rest being cast 
back into the water. We will now end this study by some observations 
upon a foreign species of oyster which it may be possible to acclimate 
in our southern waters, and which, although without value as an article 
of food, is of very great commercial importance; I refer to the pearl- 
oyster. 
The shell of this species is semicircular, greenish externally, and of 
a beautiful nacreous color upon the inside. The animal is white, soft, 
and similar in form to the common oyster. The pearls found in the shell 
of this mollusk appear to be calcareous secretions from the mantle lobes 
* A judicious fishing or working of an oyster-bed tends to increase both its size and 
value, while a natural unfinished oyster-bank, instead of being of unlimited growth, 
is always limited in size by the condition of the soilupon which it is formed as affected 
by the currents of the surrounding waters.—(Tr.) 
