294 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



bers wherever oysters grow, and are numerous in species; so tbat the 

 subject would be worthy of the attention of some one who had devoted 

 extensive study to them. By such a course it would be possible to de- 

 termine whether the diatoinaceous flora of a given district where oysters 

 are grown differed essentially from the diatomaceous flora of another: 

 and it might in this way be possible to get at the reason why oysters 

 from different localities differ in flavor. 



THE POPULAR DELUSION REGARDING GREEN-GILLED OYSTERS. 



For many years green-gilled oysters in England and France have 

 been more highly esteemed by the epicure than the white-fleshed ones; 

 in consequence of which fact the growers have made every effort to cater 

 to this singular taste. They have also found it a profitable taste to 

 cater to; because the green-gilled oysters are higher in price in the 

 markets of Europe than the white fleshed ones. The only place in the 

 United States, so far as the writer is aware, where this taste has been 

 developed is in the city of Norfolk, Va. ; where it is said that green- 

 gilled oysters are worth five cents per quart more than white-fleshed 

 ones. The prevalence of this peculiarity in a large proportion of the 

 oysters from the Chesapeake Bay and Rappahannock Eiver last winter 

 was the cause of a serious decrease iu the value of the affected product. 

 Every test, chemical, physical, and gastronomical, which has been tried 

 at the instance of various investigators, has shown that the consumption 

 of green-gilled oysters is never attended with evil effects. In fact, it 

 has been proved that the green color is in no way due to copper, as 

 has been asserted by ignorant or prejudiced persons. In truth, the 

 color is due to a harmless vegetable coloring matter absorbed from the 

 food upon which the animal feeds, and is very nearly identical in com- 

 position with the green coloring material found in the leaves of trees. 



It is to be hoped that the public mind maybe educated up to the 

 point where they will fully comprehend the fallacy of the belief that the 

 green of oysters is due to copper ; because it may be said that any such 

 quantity of a copper salt which would produce the green color of oys- 

 ters would necessarily be fatal to the animal itself. 



To sum up, it may be said that the doctrine that the green color of 

 oysters is due to copper is utterly fallacious, and without a shadow of 

 foundation in fact. 



It was formerly believed that the acquisition of the green color was 

 confined to the oyster, but I have recently learned that the soft and hard 

 clam are both affected under certain conditions and at certain times by 

 a similar alteration in the tint of the gills, which is doubtless due to pre- 

 cisely the same cause as the same condition in the oyster. This is 

 all the more likely, because the food consumed by these two animals 

 is very similar to that consumed by the oyster ; but that they should 

 be in any way deteriorated in quality by the acquisition of this green 

 color is in the highest degree improbable. 



\Yoods Holl, /September ■!, 1883. 



