performed with the hard shell clam, Venus mercenaria, failed 

 to show toxicity, probably from insufficient concentration of 

 oil nised. 



2. The toxicity of these oils is apparent whether they are present 

 as oil slicks on the surface of the water or are held on the 

 bottom bound to carbonized sand. 



3. Strongly toxic fractions obtained by shaking crude oil and 

 Diesel oil with sea water and separating the two phases shew 

 that the toxic effect is due to a substance or substances 

 leached by water. 



4. The toxicity of crude oil to toadfish embryos was found to 

 increase with concentration; the relationship may be approxi- 

 mately expressed by an ©ouation y = eixc , where y is survival 

 tlme,x is concentration, and a and o are constants, 



5* The presence in water of crude oil and Diesel oil mixed with 

 carbonized sand and of extracts of these oils interferes 

 with the pumping mechanisms of the gills of oysters and reduces 

 the rate of filtration of water* Continued exposure of oysters 

 to sea water flowing at a slov/ rate over a mixture of crude oil 

 and carbonized sand results in a marked reduction in the amount 

 of water pumped by oysters and in a decrease in the number of 

 hours that the oysters remain open* 



6* There is definite advantage in the use of carbonized sand in 



treating oil slicks for it localizes the oil pollution, prevents 

 the spread of oil over the surface of water, and subnerges and 

 permanently anchors the oil near the source of pollution. In 

 view of the fact that bottoms of harbors and bays near industrial 

 ports are grossly polluted and nonproductive, the sinking of oil 

 in these localities will not increase the damages to the fisheries. 

 It is considered that the presence of oil, bound to carbonized 

 sand, in such localities will not affect productive shellfish 

 grounds located in the nearby unpolluted areas because the dilution 

 of toxic substances would be too great and would not reach a 

 threshold concentration for harmful effects. 



49 



