[9] EXPERIMENTS IN OYSTER CULTURE RYDER. 771 



selves to the sides of the jars and the surface of the oyster shells were 

 great indeed. The valves to our surprise were found remarkably well 

 developed and had already grown so as to cover the sides of the em- 

 bryos, and from between the edges of the valves the velum could be 

 seen to protrude and be retracted at intervals. In fact within the short 

 space of twenty hours we had embryos farther advanced in develop- 

 ment than any figured by Professor Brooks in his admirable work on 

 the development of the oyster, published in 1880. 



The oyster shells in the jars in the McDonald apparatus may have 

 helped to supplj^ the necessary carbonate of lime for the rapid growth 

 of the valves of the larval oysters. It will be desirable to put this 

 matter to the test. The mode of fixation is still problematical. I even 

 doubt whether the objects which I see fixed to the inner surface of the 

 jars and aquaria by the help of a good triplet are oysters at all; keep 

 vacillating between one and the other opinion all day, because of the 

 imperfect means at my disposal to determine their true nature with cer- 

 tainty. Unfortunately I had not thought of putting small transparent 

 slips of mica or glass in the aquaria in order to afford surfaces for fix- 

 ation, which could be transferred to the stage of the microscope, with- 

 out injury to the minute and delicate embryos. The temperature of the 

 water in the ai)paratus has ranged to-day from 73° to 80° Fahr. 



July 23. — The young oysters detected for the first time fixed to the 

 sides of the jars this morning must be examined by such means as will 

 certainly establish their true nature. In order to accomplish this I 

 had our carpenter, Mr. Tolbert, make me a stand of wood to hold the 

 draw-tube objectives and eye-pieces of my microscope in a horizontal 

 position so as to view the embryos in their natural relations on the in- 

 side of the glass vessels undisturbed. I find at last, by this means, that 

 the little objects fast to the inner surface of the glass are truly oysters. 

 The pouring and lifting of the water from the lowermost to the upper- 

 most aquarium does not seem to interfere with the attachments of the 

 embryos or their development. Their mode of attachment is still a 

 puzzle. I cannot clearly discern even with a magnification of 150 times — 

 the highest I can use under the circumstances — how the attachment is 

 made.* The positions of the individuals vary ; some adhere by the 

 side to the glass and display only a profile view of themselves; others 

 are apparently swayed more or less by the current of water flowing 



[* This point I have since settled approximately in my paper entitled, " On the 

 mode of fixation of the fry of the oyster," Bull. United States Fish Commission, IT, 

 lb82, xjp. 383-387. Unfortunately the figures are reversed in the plate which accom- 

 panies that paper through, an unintentional oversight. Figs. 3, 4, 5, 6, and 7 viewed 

 from above should have the tips of the umbos directed towards the left instead of to 

 the right. Fig. 8, viewed from below, should have the beak or umbo of the larval shell 

 directed to the top of the page instead of to the bottom for a like reason. The di- 

 rection of the umbos or beaks of the larval valves of young oysters is invariably the 

 same, or to the left as viewed from above. The larval valves as well as those of the 

 spat stage are also glued to the surface of attachment, so that the existence of a bys- 

 sus seems doubtful. (January 4, 1884.)] 



