G12 SCIENTIFIC RECORD FOR 1884. 



Puys^gur's conclusious. He had ascertained that the conunon Ameri- 

 can oyster {Ostrca virginica) "is affected by an acquired viridity at cer- 

 tain times and in certain places in precisely the same way as the com- 

 mon 0. cduli.s of Europe and the 0. angulata of the Tagns," as he had 

 been able to learn from fresh material from Liverpool, obtained through 

 the efforts of Professor Baird. "The cause of this peculiar staining of 

 the soft parts of these animals is, therefore, very probably the same 

 throughout both the European and the American oyster-growing re- 

 ffious. 



V 



Mr. Eyder further extended his studies to the florula of the water 

 about the oyster beds and to the contents of the oyster's stomach. He 

 found the special oyster diatom {Kavicula ostrearum) abundant, and also 

 other diatoms, and has thus summarized his results: 



"Taking a survey of the lower groups of the vegetable world, which 

 contain bluish-green pigments, and which are at the same time free- 

 swimming in their habits, so as to place them within reach of the sta- 

 tionary oyster as food, there is none which actually seems more likely 

 to be the source of the green tinge here discussed than the Diatomaccm. 

 And as there is no other class of forms so commonly and constantly 

 met with in the alimentary canals of marine mollusks generally, I think 

 we might take it for granted, for this reason alone, that they are the 

 source of the coloration. In fact, it is rarely that I have met with any 

 other vegetable organisms in the stomachs of oysters except diatoms, 

 after having examined hundreds, by the excellent method of first re- 

 moving the recently-swallowed contents of the gastric cavity with a 

 ])ipette thrust into the mouth and through the short gullet. The 'bill 

 of fare' of the animal can then be very deliberately studied under the 

 microscope after the contents of the pipette have been pressed out upon 

 and prepared for observation under a compressorium." 



Mr. Ryder also endeavored to ascertain the elementary nature of the 

 green thus dissolved out of the diatomaceous food of the oyster. His 

 investigations could not be completed, but were carried far enough to 

 justify an opinion. This was that " the coloring material in green oysters, 

 on account of its solubility in water, its instability and color, is prob- 

 ably allied to phycocyanin, since we know that it is not chlorophyll, 

 because the latter is insoluble in water." The spectroscope, however, 

 gave him "entirely negative evidence npon tliis point." 



Mr. Ryder concludes with the assurance that the belief or fear that 

 green oysters are injurious or hurtful is without foundation. {Ann. Hep. 

 Com. Fish., (be, 1882, pp. 793-804, 1884.) 



The assumption of the Spat stage by the Oyster. — The " metamorphosis 

 and the post-larval stages of the development of the oyster" have been 

 studied and described by Mr. John A. Ryder. His memoir is a long 

 one and gives details of his methods of investigation and his various 

 observations. The results have been summarized by himself in the 

 following terms : 



