352 PROCEEDINGS OF THE ACADEMY OF [1892. 



behalf of Prof. R. C. Schiedt, of Franklin and Marshall College, 

 Lancaster, Pa., the hitter's discovery of the fact that the oysters 

 native to the northwest coast of the United States are hermaphro- 

 dite and viviparous. Specimens from the coast of Oregon and 

 Washington show that the same condition exists in the reproductive 

 follicles as in those of O&trea edulis of Europe. The presence of 

 eggs and of spermatoblasts and spermatozoa in the same follicles 

 is the invariable rule. The ova, like those of 0. edulis, are much 

 larger than those of 0. virginica, though perhaps not quite so large 

 as the former. The embryos are fertilized in the gill and mantle 

 cavities, where they undergo development. 



These northwest-coast oysters also resemble the oysters of Europe 

 in that they are small and have little or no indication of purple 

 pigment on the impression or point of insertion of the adductor 

 muscle, which is so conspicuous a feature in Ostrea virginica of our 

 eastern coast. 



On the cause of the greening of the oyster and its presumed 

 algous endoparasiies. — Prof. John A. Ryder also reported on 

 behalf of Prof. Schiedt and himself the fact that living oysters 

 from which the right valves had been removed, also became green 

 about the heart as soon as green alga3 appeared on the sides of the 

 aquaria in which the oysters were kept at Sea Isle laboratory. Our 

 experience, unlike that of Prof. Decaisne and others in France, was 

 not conclusive as to the cause beiug the bluish green pigment, 

 phycocyanin, absorbed from certain diatoms. On the contrary, 

 the forms of algse present were diatoms, desmids and the spores of 

 Ulva, and, possibly, round-celled unicellular forms, so that it 

 became impossible to decide from which species, used as food, the 

 pigment was derived that discolored the affected heart of the speci- 

 men observed to become tinged. 



Prof Schiedt now informs the speaker that some of these marine 

 algre which are believed to have caused the discoloration of the 

 oysters at Sea Isle, he has kept alive in a small aquarium filled 

 with sea water, at Lancaster, for over two months since he left the 

 sea- side laboratory. 



The occurrence of these unicellular alga^ of various kinds in 

 association with the abrupt appearance of the green color in some 

 one organ of the oyster, as happened at Sea Isle City, opens up the 

 query whether the singular brownish green bodies so often 

 observed by Prof Ryder in sections of the connective tissues of the 

 oyster are not endoparasitic algte, which are in some way genetically 

 connected with some of the forms that appeared in association with 

 " greened " oysters at Sea Isle. The late Prof Leidy's discovery, 

 many years ago, of algae in the tissues of fresh-water mussels, is 

 suggestive in this connection. 



