800 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



An examiuatiou of the digestive caual of the oysters used iu the ex- 

 periments proved that the soft substance of the diatoms was really ab- 

 sorbed. The stomach, intestine, and excrements were packed full of the 

 tests of the Naviculce. These tests, composed of silex, were not attacked 

 by the juices of the stomach, but it would have astonished us to find 

 that their contents, protected as they are by such a refractory envelope, 

 had suffered dissolution by the action of the digestive fluids of the oyster, 

 if we did not know that this envelope was not completely closed, but that 

 there is an uusilicified line of suture which separates the two valves 

 which compose the frustules of the diatoms. 



There therefore remains no longer any doubt as to the fact that the 

 viridity of oysters is entirely due to the absorption or digestion of the 

 soft parts of the NaviculcG held in suspension by the surrounding water ; 

 this definite experience also completely overturns the hypotheses which 

 attribute it to the inflnence of the soil, to the mixture of fresh and salt 

 water, to northeast winds ; in a word, all the other conjectural causes 

 to which this simple phenomenon has been childishly attributed are 

 shown to be inadequate. 



It is evident, moreover, that the coloring matter is directly absorbed 

 by the mollusks, and that the process takes place inside of the animals. 

 If, iu fact, dissolution of the coloring matter took place in sea water, 

 the water would be tinged as soon as the diatoms were blanched. Now, 

 this is not the case. In fresh water, on the contrary, the coloring mat- 

 ter is immediately dissolved and as a result the diatoms are blanched. 

 A single drop of water placed on a slide containing the diatoms causes 

 them to lose their color instantly. Finally, if a piece of filtering paper 

 is saturated in the fresh water which has been placed on the diatoms, 

 and it is afterwards dried, it will present absolutely the same color as 

 the green oysters. 



These laboratory, observations are, moreover, perfectly in accord with 

 the phenomena observed by the oyster culturists. Heavy rains cause 

 the greenness of the claires to disappear, and the dry and salt-laden 

 northeast winds, which augment the saturation of the waters, are, on 

 the contrary, favorable to the production of the green coating in the 

 claires. 



If the subject is still far from exhausted, that part of it with which I 

 have busied myself has been decided. Others who continue the re- 

 search may, perhaps, do better than I, but not by the use of other meth- 

 ods. I submit these researches to my successors, and, without further 

 comment, I would like to be permitted to call attention to the two fol- 

 lowing questions, which, it appears to me, it would be interesting to 

 study : 



1. Is 'Savicula fusiformis var. ortrearia present at all seasons of the 

 year in the claires, or is it found in winter ? 



2. The coloration, which reveals its presence during the time when 

 the claires are green, is it accidental and temporary? In other words, 



