20 30 



Concentration of Oil 



40 



50 



Figure 6. Mean survival times of an oceanic pteropod mollusc Creseis acicula in 

 various concentrations of water soluble and reaction of No. 2 flel oil (Exxon Bay- 

 town). 



exposure. It is demonstrable that many of the aromatic compounds 

 occurring in petroleum oils are harmful to marine animals, and rela- 

 tive toxicities of some of them have been determined. Here, however, 



35 



