122 American Fisheries Society 



No difficulty was experienced in keeping the fish during exper- 

 iments. Trout fmgerlings* were used and during experiments 

 were kept in battery jars containing 1500 cc. of water to which 

 the substance in question had been added. The water was aerated 

 by means of a constant stream of air being passed through it. 

 The experiments were performed in an unheated room and in 

 very cold weather freezing of the water was prevented by heating 

 the air before passing it into the jars. The air supply was obtained 

 by connecting a filter pump with a bottle having two outlet 

 tubes, one extending to the bottom, through which the water was 

 forced out, and one from the top through which the air was dis- 

 tributed to the jars. When necessary to heat the water the air 

 was passed through another bottle in which there was an electrical 

 heating unit, before admitting to the jars containing the fish. A 

 thermoregulator was connected with the heating unit and placed 

 in one of the jars which prevented the temperature exceeding 15° C. 

 In control experiments where no tar was added to the water the 

 the fish would remain in a perfectly healthy condition for weeks. 

 The only disturbing influences were the products of metabolism, 

 and growth of bacteria. These were eliminated by renewing the 

 solutions once a week during cold weather, and after each feeding 

 in warmer weather. 



The trout were fed on chopped liver. Those in the tank 

 where the stock was kept never refused food, but those in the 

 jars to which some of the tars had been added refused food at times. 



Some of the substances were extremely toxic to fish, others 

 less so and some had no effect. The degree of toxicity seemed to 

 depend, in most cases, largely upon the degree of solubility in 

 water. 



Following are some of the results obtained in experiments in 

 which the samples sent from the Office of Public Roads were 

 used. The description of the samples is that obtained from that 

 office. 



"No. 5899 consists of some of the higher boiling distillates of 

 petroleum, flash point 148° C, burning point 178° C, presumably 

 obtained from Indiana or Illinois crude petroleum." 



* Through the courtesy of the Massachusetts State Fish and Game 

 Commission, the trout were secured from the State Hatchery at Wilkins- 

 ville, Mass. 



