PEOGEESS IX BIOLOGICAL II^QUIEIES, 1921. 33 



The study, made in cooperation with the Bureau of Chemistry, 

 of the trade-waste problem in its rehition to oyster culture was 

 continued. Before he left the Bureau Dr. Churchill perfomied 

 experiments with various dilutions of standard solutions of chemi- 

 cals known to occur in or to be discharged into water near 03'ster 

 beds. He found the larvae very sensitive, certain chemicals being 

 fatal even in great dilutions. In Bridgeport Harbor late in the 

 season samples were collected for the determination of the distribu- 

 tion of injurious wastes, particularly the heavy metals. As a result 

 of the study of this harbor and of the efforts of the two bureaus, 

 the company, which discharged much the greatest amounts of copper, 

 was persuaded to install an electrolj'tic recovery process, which has 

 given great promise both as a money saver and as a means of im- 

 provinjr harbor conditions. 



In »Jiine, 1921, the spawning of oysters in Great South Bay has 

 been found to begin in earnest almost a month earlier than in pre- 

 vious years of our experience and to occur at decidedly lower tem- 

 peratures. The work is being so carried on as to check up the data 

 obtained in 1919, and already the larvae have been found to be much 

 more widely distributed in good num])ers. In addition, as ©impor- 

 tunity permits, data are being gathered to test out the hypothesis 

 advanced by Dr. T. C. Nelson that oyster larvae of the larger sizes 

 keep from being washed to sea by sinking with the ebb tide and 

 rising with the flood. 



The study of the development and distribution of the larvae is 

 of interest to local oystermen and has, it is believed, influenced 

 them in determining the times, places, and extent of planting shells 

 for set. The immediate purpose of the Bui-eau, it must be under- 

 stood, is to determine the possil)ilities of the method of larvae survey 

 in obtaining best results and effecting economies in planting and in 

 the prevention of costly wastes from j)lanting in seasons when a set 

 is not obtainable. Once a satisfactory demonstration is obtained, 

 the method can be applied in otber localities as well as at the places 

 where the experiments have been conducted. 



EFFECT OF roLLlTIOXS II'OX ri{()I'AC;ATIf)X OF OYSTERS. 



Pollutions may affect oyster eggs and larvae, either directly, by the 

 toxic effect of certain chemicals ui)on the young oysters, or indirectly, 

 through the exhaustion of the oxygen supply tlnd partial or com- 

 plete suffocation of the larvae. The latter aspect of the problem was 

 given attentif)n by Dr. P. H. Mitchell, director of the Woods Hole 

 (Mass.) Fisheries laboratory. 



In experiments on the effect of oxygen deprivation on oyster larvae 

 Dr. Mitchell founrl that while the embryos are sensitive to dimin- 

 ished oxygen supply a number of factors affect the loAvcr limit of the 

 oxygen content of water compatible with life of the larvae. The 

 factors noted were: (a) The previous history of the eggs from which 

 the hirvan.were hatched, for exainj)le, ri])eness at the time of artiflcial 

 fertibzation and previous exjjosure to polbition; (h) the age of the 

 larvae; (c) the carbon-dioxide content of the water; (r/) the hydro- 

 gen ion concentration of the water; and ((') the temperatuie. 



Development of a satisfactory technique for handling such un- 

 Wsually .sensitive and perishable material as oyster larvie, in the 



