[15] EXPERIMENTS IN OYSTER CULTURE RYDER. 777 



unfavorable for our work. Embryonized ova in aquaria all have died 

 and begun to disintegrate. 



August 7. — I had a large lot of oysters opened to-day; some of theiu 

 from the deeper water of the bay. The spawn appears scarce and poor 

 in quality, judging by the physical tests already described. I fertilized 

 another lot of eggs at 11 a. m. Temperature of the water to-day has 

 ranged from 87-9Uo Fahr. 



August 8. — Embryos of yesterday's lot mostly dead. A lot impreg- 

 nated to-day at 2 p. m., which were apparently in very fine condition at 

 3 p. m., in water of specific gravity 1.009, or that usual in Saint Jerome's 

 Greek. Put aquarium and closed circuit in operation with water of a 

 specific gravity of 1.013. Temperature, 80° Fahr. 



August 10. — Upon making an examination of the aquaria and closed 

 circuits to day I find a very few embryos of the 8th still alive, but weakly, 

 with vesicular watery prominences apparent on their surfaces. Vast 

 numbers of a brownish diatom have now made their appearance, espe- 

 cially in one of the aquaria, in association with Amceha radiosa. 



August 11. — I made the last examination of the apparatus to-day. 

 The diatoms which were observed yesterday are now more numerous 

 than ever in the incubating apparatus. They are brownish, with a boat- 

 shaped central portion, with a styliform prolongation at either end. It 

 is the same type of diatom, the silicious tests of which I have found 

 more abundantly than any other in the intestine of the adult oyster. 

 They have multiplied with enormous rapidity, showing that it was not 

 the purity of the water which was lacking to favor the growth of the 

 oyster embryos. The latter have entirely disappeared, in spite of the 

 careful search instituted for the purpose of finding them. The fine lot 

 of eggs fertilized on the 8th instant have amounted to nothing. 



In order to see if I could catch some natural spat in the oyster pond 

 I had a frame constructed to hold a number of panes of ordinary win- 

 dow glass. The frame was arranged to float, and had the bottom closed 

 with a coarse wire screen. Upon this wire screen I placed a number of 

 spawning oysters, then arranged the glass plates above them and left 

 the structure floating from a temporary anchorage provided. for the pur- 

 pose and arranged for the convenience of the observer in making the 

 examination of the collector. I found, however, that a large amount 

 of gelatinous, transparent, slimy matter soon covered the plates of glass. 

 This slimy matter I found, as I had previously learned, waslargely com- 

 posed of the lowestand most destructive vegetable organisms — Vibriones, 

 Bacteria, and Micrococci — which I did not determine with precision. 

 After failing, during several examinations, to find any young oyster fry 

 or spat, I abandoned the project for the time being, with the hope that 

 I might resume the investigation at another time. My object was to 

 get the fry to adhere to some transparent basis upon which 1 might ex- 

 amine it with the microscope in a natural and undisturbed condition. 



Our observations closed with this date. We left the station on the 

 next day — the 12th of August. 



