796 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [4] 



properties of this matter as well as its color are very dififerent from tlie 

 latter. 



M. Bouchou-Brandely, charged in 1877 with the duty of preparing a 

 Rapport snr V ostreiculture sur le littoral de la Manclie et de V Ocean, reviews 

 briefly the method of culture by which oysters are made to assume this 

 color, but does not touch upon its causes. He thinks it probable that 

 the coloration is due to the absorption of the chorophyll diffused through 

 the sea-water, an opinion which is without foundation, because chloro- 

 phyll, which is soluble in alcohol, ether, benzine, &c., is altogether in- 

 soluble in water. 



Finally, M. Paul Petit published an article in the Revue Pharmaceu- 

 tique for 1878, No. 7, page 112, from which we extract the following : 



"The learned French diatomologist, M. A. de Brebisson, has observed 

 in the oyster parks of Courseulles a peculiar diatom to which he has 

 given the name of AmpMpleura ostrearia. 



"This species assumes in the portion not occupied by the endochrome 

 a bluish- green tint, but this disappears after dessication. We have sup- 

 posed, says M. de Br6bisson in the note which accompanies his drawing, 

 that this species communicated its color to green oysters, and that it 

 seemed to him that it assumed this color when it grew in a i3ark, which 

 had a tendency to cause the oysters contained therein to become green." 



In the begiuning of his article, M. Paul Petit mentions the analyses 

 made by M. Balland, pharmacist-major, and M. Gaillard, chief pharma- 

 cist of division, at Alger, and who declared that they had found copper 

 in green oysters. M. Gaillard himself concludes from his observations 

 that this was because some process wtis fraudulently employed to color 

 the mollusks, and that it consisted merely in immersing them in a solu- 

 tion of a salt of copper, and leaving them in it till they were saturated 

 by it. 



We will not deny that these chemists may have found copper in these 

 oysters, since they make the assertion, but our own direct experiments 

 have shown — 



1. That an oyster which is placed in a bath of sulphate of copper is 

 not colored at all. 



2. That death quickly follows when they are plunged into such a mix- 

 ture. — 



I think I have now completed the historical review of the researches 

 which have been made up to the present time to discover the causes of 

 the greening of oysters, and I hope I have shown that none are verj^ ex- 

 haustive, the truth still remaining to be discovered in regard to this 

 subject ; but, before passing to the observations and experiments which 

 we have made jointly, I would give expression to my sense of obliga- 

 tion for the friendly and able assistance which was very willingly ren- 

 dered to me during his stay at Croisic in the spring of 1877, by Dr. 

 Bornet, the distinguished algologist, well known to the learned world, 

 and as the coutinuator of the labors of the lamented M. Thuret. 



I received a commission in 1875 from the department of the marine 



