The toxic action of oils on molluacem larvae has been pointed out, 

 by Welson (1921). He states (page 3) "A film of oil on the surface of 

 the water will kill molluscan larvae within a few hours, owing; largely 

 to their habit of swimning close to the surface." This statement was 

 based on laboratory experiments, which are discussed by him in a later 

 paper (Nelson, 1925, page 178). He continues with "Such larvae of 

 shellfish as escape the oil at the surface will, when the time comes 

 to attach to the bottom, find this unsuitable on account of the oil which 

 is accumulated there and will therefore perish." It seems apparent that 

 harmful effects on the larvae and young of oysters could be expected. 

 Tests were not included in Hie present report on any but adult animals. 



Otir observations of the toxic effects of oil are in agreement with 

 the data reported by earlier investigations. European students of this 

 problem attributed the toxic effect of the Baku petroleum to the presence 

 of naphthenic acids, which they found to be fatal to daoe and ruff 

 (small European peroh) in concentrations varying from 4 to 16 parts per 

 million (quoted from Seydel, 1913). Crayfish weighing 35 grama was 

 killed in 18 to 60 hours in the solutions of 5 to 60 mg. per liter. 

 Among various materials of refinery wastes listed by the IT. S. Public 

 Health Servioe (1939) as destructive to aquatic life, mention is mad« 

 of phenol, inJ\irious to trout and goldfish, and naphthenio aoids, whioh 

 killed minnows in 72 hours in a concentration of five parts per million. 

 Naphthenio acids may be extracted from crude oil or distillates by aqueous 

 NaOH solution in whioh the acids dissolve, yielding sodium naphthenates 

 (Ellis, 1934)* Mention should be made here also of the results of many 

 experiments conducted in England on the damages to fisheries by various 

 tars used for road surfacing (Ministry of Transport and Ministry of 

 Agriculture and Fisheries, 1950). Laboratory tests conducted jointly 

 by these agencies demonstrated the toxicities to fish of the extracts 

 of tar and various heavy oils (1. c, p. 131). In a recent paper 

 Veselov (1948) has described experiments showing an extremely marked 

 toxicity of Ischimbaev crude oil in concentrations as weak as o.4 ml. 

 of oil per liter of water to small fresh-water fish ( Carassius oarassius L)' 

 Water soluble fractions, obtained by shaking 15 ml. of crude oil in a 

 liter of water for 15 minutes, were found to be highly toxic also. 



Many of the oils when shaken with water form emulsions, both water 

 and oil, and oil in water. In personal communication to P. S. Galtsoff, 

 Dr. C. E. Coates (1936) states that he had an emulsion of oil and water 

 which stood for ten to fifteen years without separating completely. He 

 points out that in passing through the gills of the oyster these emulsoids, 

 caught by the cilia, may produce anything frcm sickness to death. This 

 point is of great interest and requires further study. From the point 

 of view of conservation, the question of the physical status of the oil 

 mixed with water is, however, of little importance. The fishery biologist 

 is primarily concerned with the toxicity of oil, and the question whether 

 the poisonous effect is caused by water soluble fractions of oil or by 



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