[9] CAUSE OF THE GREENING OF OYSTERS. 801 



does this alga disappear completely from tbe claires wlicn tlie waters 

 change their color, or does it only lose its color at this time ? 



These difficult questions which involve the consideration of t>he mar- 

 velous world of protophytes, require for their resolution much patient 

 observation. But the difficulty of the problem only augmented the en- 

 joyment of those engaged in its solution, and to conclude with an ex- 

 pression familiar to my sympathetic collaborator, 1 would say : we dis- 

 covered all that we sought; that sufficed for the pleasure of the seeking. 



SUPPLEMENTAEY NOTE ON THE COLORATION OF THE 

 BLOOD CORPUSCLES OF THE OYSTER. 



By John A. Ryder. 



The foregoing essay by M. Puys6gur has just recently fallen into my 

 hands; earlier references which I made to his important investigations 

 have been only at second hand and from notices which have not done 

 his work justice. His methods have been positive, and there seems to 

 have been little chance for him to have erred in his conclusions. 



My own investigations of this subject have also convinced me of the 

 correctness of M. Puysegur's conclusions; they, in fact, supplement 

 them. I subjoin a brief statement of the facts observed by me, together 

 with some account of collateral observations by other investigators. 



I have ascertained that Ostrea virginica is affected by an acquired 

 viridity at certain times and in certain places in precisely the same way 

 as the common 0. edulis of Europe and the 0. angulata of the Tagus, 

 as I have been able to learn from fresh material from Liverpool, ob- 

 tained for me 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 regions. My own studies have also shown beyond a 

 shadow of doubt that the acquisition of this color comes about as fol- 

 lows: That the coloring is either derived from without, or else may be 

 a hepatic coloring principle, which, on account of some derangement of 

 the normal metabolic processes of the animal, has been dissolved and 

 absorbed by the lympho-haemal fluids, and then imbibed by the blood 

 cells or haematoblasts, and thus imparted to them their peculiar color. 

 The blood cell of the oyster measures about ^ooth of an inch in diam- 

 eter, but varies somewhat in size. It is amoebal in its behavior to a 

 surprising degree, and throws out pseudopodia when at rest, which may 

 even be branched. In a temperature abnormal to them in winter, that 

 is, in a very warm room, I have had them live under a compressorium, 

 bathed in the serum from the vessels of the animal, for four hours, dur- 

 S. Mis. 46 51 



