406 



Table III 



*Affected but did not die. 



In nearly all the experiments tried the fishes were positive in re- 

 action to ethylene, often being overcome in the gradient, and even dy- 

 ing without showing any avoidance of the ethylene water. 2, 30, and 

 60 cc. per liter (2, 30, and 60 pts. per million) were tried with similar 

 results; the only suggestion of a negative reaction came in the lowest 

 concentration (Chart V, graph 50). 



Amylene. 



It occurs in coal-tar but only in small quantities. Amylene was 

 once used as an anesthetic but was found to be dangerous. It acts as an 

 anesthetic on fishes. Various fishes are positive to it in all concentra- 

 tions tried (Chart V, graphs 48 and 49). 



Methane. 



Methane is one of the most abundant constituents of illuminating 

 gas. It was made by the action of soda lime on sodium acetate and 

 washed in water. Crocker found that methane made that way was 

 not toxic to plants while other methods yielded toxic products. 



It is not toxic to man and no toxic effects were noted for fishes 

 except in the case of a single specimen of Lahidesthes siccidus. 



VII. General Discussion. 



I. TOXICITY AND SIZE- 



One of the very important questions arising in connection with the 

 toxicity of substances to fish is the relation of age and size of the 

 fishes to their resistance to the substance. In general, with the ma- 

 jority of compounds studied the largest fishes survived longest. While 



