BULLETIN OF THE UNITED STATES FISH COMMISSION. 443 



l30.-OiV THE AKTIFICIAT. PBOPACATIOIV A1V» CUI>TI VATIOIV OF 



OVWTEKS IIV FI.OATS. 



By Prof. W. K. BROOKS. 



[From Johns Hopkius University Circular, Vol. V, No. 43.] 



Without expressing any opinion as to the value of the process of 

 "fattening" oysters by placing them for a few days in cars floating in 

 fresh water, I wish to point out that there is no similarity between this 

 process and the process of propagation which is here descnbed. 



My attention was first called to the value of floating cars in oyster 

 culture by Mr. William Armstrong, of Hampton, Va., who informed 

 me, in 1884, that "seed" oysters which he had placed in floating cars 

 in the mouth of Hampton Creek grew more rapidly, and were of a bet- 

 ter shape and more marketable, than those which grew from seed planted 

 on the bottom in the usual way. 



One of the results of my study, in 1879, of the development of the 

 oyster was the discovery that there is a period of several hours, imme- 

 diately after the embryo acquires its locomotor cilia, when it swims at 

 the surface, and this is the period when it is swept into contact with 

 collectors. As soon as the shell appears the larva is dragged down by 

 its weight, and either settles to the bottom and dies or swims for a time 

 near the bottom. The tendency to swim at the surface is an adaptation 

 for securing wide distribution by means of the winds and currents, 

 which sweep the young oysters against solid bodies which may serve 

 for attachment; and the greatest danger to which the oyster is exposed, 

 at any part of its life, is that it may not, at the swimming stage, find a 

 clean, hard surface for attachment. 



As it is microscopic and only about half as thick as a sheet of thin 

 paper, it may be smothered by a deposit of sediment or mud so light as 

 to be invisible, and most of the failures to get a good "set of spat" are 

 due to the formation of a coat of sediment upon the collectors before 

 the young oysters come into contact with them. 



It occurred to me this summer that this danger could be entirely 

 avoided by the use of floating collectors, for little sediment can fall on 

 a body which is close to the surface of the water, and most of this will 

 be swept away by currents, which will, at the same time, sweep the 

 swimming embryos down into the collector, and thus insure an early, 

 abundant, and successful "set." 



I accordingly constructed a floating car, made so as to permit the free 

 circulation of the water. This was tilled with clean oyster-shells and 

 moored in the channel in front of the laboratory at Beaufort, N. C, on 

 July 4. As all the oysters in the vicinity were in very shallow water, 

 they were nearly through spawning, and the conditions were therefore 

 very unfavorable; but, notwithstanding this, I immediately secured a 



