403 



not general among fishes dying in waste. This is probably due to the 

 irritating character of the substance. The toxicity of the water con- 

 taining it is retained for several weeks, depending on the concentra- 

 tion at the beginning. Sixty-five parts per million will still produce 

 fatal results after a month's exposure in the battery jars. Weigelt 

 killed a tench in a 0.05% solution in 15 hours. Hofer ('99) obtained 

 results which more nearly resemble' mine. 



Several species of fish which were tried in the gradient tank gave 

 positive reactions to concentrations which would kill them in two or 

 three hours (in both acid and alkaline water). Orange-spotted sun- 

 fish are indifferent to very weak concentrations (Chart IV, graph 37; 

 Chart V, graph 57). 



Crcsols. 



Orthocresol is less caustic than phenol but was found to be more 

 poisonous to fishes. Fishes of various sorts were negative or indefinite 

 to concentrations about twice that recjuired to kill them in an hour, 

 but were sometimes positive to weaker fatal concentrations ( Chart IV, 

 graph 38). 



Paracrcsol is a little less toxic than phenol. A solution which 

 killed small fishes in 20 minutes, killed similar fishes in less than 12 

 hours after 2 months exposure to air in a 5x8 battery jar. Fishes 

 were uniformly positive or indifferent in both strong concentrations 

 and very weak ones (Chart IV, graph 39; Chart V, graph 56). 



Mctacresol is least toxic of the four representatives of the group. 

 The erratic convulsive movements often occur when intoxication sets 

 in. Various fishes are variable in their reaction to fatal concentra- 

 tions, but commonly when negative at the beginning of the experiment 

 the protective reaction breaks down due to the paralyzing of the sen- 

 sory nerve endings (Chart IV, graph 40). 



Phenanthrene. 



It is found in the last fractions of the distillation of coal tar "oils". 



For the experiments on fishes a quantity of it was placed in a five 

 gallon bottle of tap-water and warmed and shaken from time to time 

 during several days. This solution was used for most of the fish ex- 

 periments. In December, 1915, two liters of distilled water were 

 placed in each of three bottles. Phenanthrene was added to one to 

 make 100 mg. per liter, to another to make 5 mg. per liter, and to the 

 third to make 2.5 mg. per liter. These were allowed to stand with 

 occasional shaking till August, 1916. At this time there were still 



