756 KEPOET OF COMMISSIONER OF FISH AND FISHERIES. [16] 



rapidly than the lower or attached one, it is probable that the empty 

 shells noticed by Brooks had been attached until the oyster died, aud 

 the survival of the embryo until 1 hat stage was reached (point of attach- 

 ment) must have been due to the supply of food being approximately 

 sufficient, as I did not notice any embryos in a similar state of develop- 

 ment except in those experiments in which we attempted to increase 

 the available amount of food. In future experiments in this direction 

 the attempt must be made to supply bacteria unaccompanied by sedi- 

 ment or large quantities of water. Otherwise there will be but a re- 

 newal of our experience of the past season. 



Time and place of attachment. — The experiments of the past season 

 have thrown some additional light on this subject, and have confirmed 

 my i^revious impressions gained during the surveys of the oyster beds 

 of the Chesapeake Bay. There is but little doubt in my mind now that 

 the young fry will prefer the lower or more secluded points or surfaces 

 in selecting a j^lace for permanent fixation. I observed in 1879, in the 

 Chesapeake, that the lower sides of the collectors I placed on the beds 

 secured a much larger "set" of young than the upper. As disturbing 

 influences may have x)revented the continued life of the young attached 

 to the upper sides, and as those sides were more accessible to the va- 

 rious enemies of the young, I hesitated in deciding that the large num- 

 ber of oysters discovered on the lower sides was due principally to the 

 natural habits of the embryo; but mj- observations at Beaufort aud 

 Fair Haven indicate that such is really the case. It was uniformly 

 noticed, both by Brooks and myself, that the largest number of embryos 

 was always found on the lower side of the shells placed in the jars 

 and plates, and this difference was quite sufficient to be remarkable, 

 even had not our attention been directed to it primarily. 



As to the time of attachment, we were unable to obtain any positive 

 evidence, but incidentally I observed certain peculiarities of attach- 

 ment both at Beaufort and Fair Haven which are significant. Dr. 

 Brooks states that after the eggs have passed through the various stages 

 of segmentation and have developed cilia, the embryos swarm to the 

 surface, remaining there for a limited i)eriod and then swimming about 

 thn ugh the entire volume of water. Our observations at Beaufort and 

 my own at Fair Haven confirm the truth of Brooks' statement, and it 

 is hardly necessary to allude to it, but that I wish to call attention to 

 the fact, and to the peculiar movements of the embryos during this 

 stage of their existence. While at Fair Haven I had constantly under 

 observation many different lots of embryos in this stage, and the uni- 

 formity of their movements attracted my attention. If a large number 

 are collected in a deep beaker and held up to the light they will be 

 seen as a cloud of dust, permeating the whole volume of water. In a 

 few moments a dense film of embryos will be found at the surface of the 

 water; sometimes this is so thick that it becomes opaque when looking 

 through the bottom of the beaker. If the beaker is jarred so as to 



