234 



MORRIS M. WELLS. 



Bluegill. 



Bull-head. 



Crappie. 



Bluegill. 



Bluegill and 

 Bull-heads. 



Bull-head. 



be" 



I", ^ 



t/2 



TtU 



. 

 be " 



55 



Control. 



CHART I. 



Showing the reactions of the fishes to different degrees of acidity. The gradient 

 is between the two kinds of water, indicated at the top of each graph. Numbers 

 at the left of the chart indicate time in minutes. Strongly acid = 18 c.c. CCh per 

 liter; moderately acid = 8-10 c.c. per liter; slightly acid = 2-3 c.c. per liter; 

 and neutral water = actual neutrality to i c.c. per liter. Dotted lines indicate 

 that fish was driven. 



(c) Reaction to Acidity in Distilled Water. The distilled water, 

 which was available in quantity from the chemistry department, 

 was not rapidly toxic to the fishes and since the foregoing results 

 are of some general biological importance, it was decided to repeat 

 the experiments in distilled water. This water was faintly acid 

 with CO 2 containing 2-3 c.c. per liter. It contained no salts ; so the 

 addition of a strong acid resulted in no complications such as those 

 discussed in the case of the tap water. A number of experiments 

 was performed with various strengths of acid and alkali. The 

 neutral portion of the tank was kept track of by means of titra- 

 tions and the reactions of the fishes to this neutral region es- 



