REACTION AND RESISTANCE OF FISHES. 



237 



my experiments, I found also that the fishes do not react to this 

 alkali with the precision found for the other alkalies used. 



CHART II. 



Showing the reactions of the fishes to alkalies. The gradient was between the 

 two kinds of water indicated at the top of each graph. Strongly acid water = 18 

 c.c. CO2 per liter; and moderately acid = 8-10 c.c. per liter. Numbers to left = 

 time in minutes. 



In the first experiments a .005 N solution was run into one 

 end of the tank. The fishes selected the middle of the tank for 

 the most part, though one blue-gill was positive to the ammonia 

 end. The concentration of OH ion was of course very low, 

 with so small a concentration of so weakly ionized a base, and 

 since other experiments have shown that blue-gills are less 

 negative to neutrality than are other fishes, this reaction is not 

 surprising. The ammonia concentration was raised to .01 N 

 and the fishes, blue-gill included, moved toward the tap-water 

 end of the tank. Later the concentration of the alkali was 



