284 FOUNDERS OF OCEANOGRAPHY 



of Forth. ; and now we buy back from the French ostreo- 

 culturists the descendants of our own oysters to replenish 

 our neglected and depleted beds. It is an object-lesson in 

 the value of aquiculture. 



The further rearing and preparing for market of the oysters 

 produced at Arcachon takes place farther north, on the 

 west coast of France, in the neighbourhood of La Rochelle, 

 Marennes, and Le Croisic. In these and many other places 

 along that flat coast there are large, shallow ponds, or 

 " claires," into which sea-water is brought by means of canals 

 with sluices, so that the "claires," in some cases several 

 miles inland, may be filled at high spring tides and remain 

 as areas of stagnant sea-water, becoming warmer and denser, 

 and more and more occupied with Diatoms and other 

 vegetation, as the days go on, until the next high tide affords 

 an opportunity of refreshing the water. In this somewhat 

 artificial environment the half-grown oyster from Arcachon 

 is highly nourished, rapidly increases in size, and becomes 

 fat, soft, and luscious. Moreover, in certain "claires" the 

 process known as " greening " takes place. The gills and 

 certain other parts of the oyster acquire a bluish green 

 colour, which is probably due to the pigment in the Diatom 

 Navicula fusiformis variety ostrearia, which abounds in these 

 "claires" and upon which the oysters feed. Such green 

 oysters (" huitres vertes de Marennes ") are highly esteemed 

 in the Parisian and some other markets. 



The final stage in the preparation of the oyster is to 

 cleanse it from impurities, decomposing organic matter, 

 and possibly germs, by placing it for a few days in clean 

 tiled tanks, known as " bassins de degorgement," in which 

 the pure sea-water is frequently renewed, so as to wash away 

 aU deleterious matter. 



Oysters, mussels, and other shellfish are, of course, liable, 

 from the nature of their food — microscopic particles carried 

 in from the water or the mud close to land — ^to become 

 infected with various bacteria, including, it may be, if there 



