138 BULLETIN OF THE BUREAU OP FISHERIES. 



to remain in the tanks after the growth of the diatoms had ceased, the oysters would 

 arrive gradually at their normal color in three or four weeks. Furthermore, Gaillon 

 pointed out that common chlorophyll was not the coloring matter. His conclusion that 

 the Navicula ostrearia was the cause of the greening of Marennes oysters was accepted 

 and corroborated by other European biologists later in the century. Gaillon, how- 

 ever, offered no proof as to how the green substance reached the gills. He noticed 

 that no other organs of the body except the gills and palps were ever colored, but he 

 did not try to show how the coloration took place. He intimated that perhaps the 

 green substance entered the gills through the gill filaments, but he could not offer scien- 

 tific evidence of such entrance. 



Valenciennes in 1841 drew attention to the fact that beside the gills and palps, the 

 liver and intestines often showed a green tint, while the heart, reproductive system, 

 muscles, and blood showed no abnormal color whatsoever. 



Gaillon, in a second paper in 1824, suggested what appeared to be the proper explana- 

 tion of the green colorations in the gills, palps, liver, and intestines by saying that the 

 coloring material is taken into the alimentary canal and that the oyster's gill tissue 

 selects and deposits the coloring matter much the same as the osseous tissue of pigs fed 

 on madder selects and deposits the red coloring of that plant. Thus it will be seen that 

 Valenciennes in 1841 was hardly more than corroborating the work done by Gaillon in 

 1 82 1 and 1824. Valenciennes, however, did considerable work on the chemistry of the 

 pigment. He found that the coloring material of green-gilled oysters was insoluble in 

 water, alcohol, ether, weak alkalies, or weak acids and that the only reagents that would 

 dissolve the pigment were those that destroyed it forthwith. He, furthermore, came to 

 the conclusion that the green-gilled pigment had no connection whatsoever with any me- 

 tallic element, thus putting the green-gilled problem in a different category from the 

 copper-green oyster with which it had oftentimes been confounded. 



In 1 86 1 Coste brought forth the suggestion that the greening of Marennes oysters 

 was due to iron salts in the soil on the bottoms of the claires. This theory had been 

 advanced several times, but Bomet and Ad. Chatin showed without much doubt that 

 in certain places the oysters in the claires would remain indefinitely white and then, 

 suddenly, would take on the green coloration, due in their estimation to a change in the 

 flora of the park and not because of the fact that the floor of the claire had changed in 

 its elemental composition. Sullivan in 1870 came to the conclusion that green-gilled 

 oysters contained no copper. Dyer in 1877 showed that oysters put in dishes that con- 

 tained Navicula ostrearia became green in 36 hours. Puysegur in 1880 published the 

 results of some of his observations on greengills, mentioning especially that he had 

 turned the gills of normal oysters green by immersing the oysters for only a few hours in 

 water that contained the Navicula. Bomey, Ducaisne, and others observed the same 

 results from similar experiments. 



In 1886 Ray Lankester, the eminent Enghsh biologist, affirmed the work of Valen- 

 ciennes as regards the absence of any metalUc compound in the green pigment that caused 

 the gill coloration. In this paper Lankester made it his purpose to demonstrate three 

 things : 



1 . That the oysters do swallow the Navicula ostrearia. 



2. That a pigment having the same peculiarities determined by Valenciennes, or 

 from which Valenciennes's pigment could be derived, actually occurs in the Navicula 

 ostrearia. 



