568 REPORT — 1891. 



documents previously quoted to throw discredit upon the 

 system. The system, however, cannot be held responsible for 

 the failure that resulted from this experiment. The circum- 

 stance that did lead to the failure reported was evidently the 

 error in judgment in applying the principle on so extensive a 

 scale to the culture of a species of oyster differing materially 

 in form, habits, and methods of propagation from the European 

 type. In dealing with a matter of this sort it is, before all 

 things, desirable to proceed cautiously, and, as it were, to feel 

 one's way. In this particular case the knowledge obtained at 

 the sacrifice of so lai'ge an amount of capital as £10,000 could 

 doubtless have been gained by an expenditure of from £50 to 

 £100. 



The claire system of culture adopted by Mr. Holt is 

 prosecuted in France for fattening and the development only 

 of particular qualities in the mud-oyster (Ostrea ediUis), and not 

 for the propagation of the species. Properly constructed, these 

 claircs are in the form of shallow ponds, of from 12in. to IBin. 

 in depth, and so connected with the sea by means of sluices 

 that fresh streams of salt water obtain access to them at spring- 

 tides only. Throughout the intervening periods the water is 

 completely stagnant, and it is, I think, very questionable if the 

 Australian rock-oyster {Ostrea glomerata) could be induced to 

 thrive under such conditions. The French oysters are dis- 

 tributed in these claires at distances of about 5in. or Gin. from 

 one another, so as to allow sufficient space for each individual 

 to obtain an ample supply of food. This food consists chiefly 

 of the microscopic plants known as diatoms, which are so 

 abundantly developed in the shallow tranquil water of the 

 claires as to form a greenish scum over the surface of the mud 

 on which the oysters are placed. In course of time this 

 particular food imparts to the flesh of the oyster a distinct 

 greenish colour, which has been found by analysis to be due to 

 the presence of chlorophyl, or the essential green colouring- 

 matter of plants. A period of at least two years' culture in 

 the claircs is occupied in imparting to the oysters the full 

 green hue and prime condition for which they are so justly 

 famous. Marennes, on the Eiver Seudre, is above all places 

 celebrated for oysters thus cultivated, and the brand known as 

 the "vraies huitres vertes de Marennes" obtains a specially 

 high price in the Paris market. 



Although it is doubtful if the Australian rock-oyster would 

 lend itself to culture in the manner just described, or whether 

 under such conditions it would acquire that superior quality 

 which would command for it a price that would repay the cost 

 of production. New South Wales possesses in her waters a 

 variety of the mud-oyster {Ostrea cdulis var. angasi) that 

 should be perfectly amenable to this method of treatment. 



