RESISTANCE OF FISHES. 



327 



water had filled all the bottles and had been running through 

 them for some time, during which time the corks of all the 

 bottles had been sealed with modeling clay, it was again tested 

 for concentration and constancy of dissolved gas. The samples 

 were usually collected at the exit tube of bottle C. If the tests 

 showed the desired concentration to be present and constant, 

 fishes were quickly introduced, the corks rapidly replaced and 

 reseated, and observations begun. Because of the fact that at 



FIG. i. Showing the arrangement of the catch bottle A and the experimental 

 bottles B and C. In .4 the inlet and outlet tubes are so arranged that bubbles of 

 undissolved gas are retained in the bottle. In B and C the inlet tubes lead the 

 water to the bottoms of the bottles. The outlet tubes reach only to the bottoms 

 of the corks. This insures thorough mixing of the water and thus conditions 

 throughout the bottles are the same while the water is flowing through. 



the beginning of an experiment one set of fishes usually de- 

 manded the entire time of the observer, but one set was intro- 

 duced at a time. The second set was introduced and observed 

 after the first set had passed through the first and more vigorous 

 stages of the succumbing process. 



In order to make certain that the water as it passed through 

 bottle B was not affected to a measurable extent, by the presence 

 of the fishes, a number of tests were made of samples collected 

 at the exit tube of bottle B. None of these tests showed any 



