REACTION AND RESISTANCE OF FISHES. 235 



pecially noted. The results are presented in Table 1 1.; in brief 

 they are as follows. The fishes spent practically all the time in 

 the acid portion of the tank, turning back from the alkaline end 

 at a point just on the acid side of neutrality. They did not, how- 

 ever, select the highest acidity available, but swam back and 

 forth in the tank betAveen neutrality on the one hand and about 

 .OOO2N HoSO4 on the other. The small amount of COa present 

 in the distilled water may be neglected in the presence of the 

 much more ionized acid. At the range of dilution used in these 

 experiments, carbonic acid would have to be about 1,400 times 

 as concentrated as sulfuric acid, to give an equal concentration 

 of H ion. 



TABLE II. 



SHOWING THE REACTIONS OF FISHES TO ACIDITY AND ALKALINITY IN DISTILLED 



WATER. 

 Acid 

 Used. Concentration. Reaction. 



.00004 N Negative: choose higher acidity. 



.0001 N Positive: some fishes choose this concentra- 



tration in preference to either higher or 

 lower acidity. 



H2SO4 .0005 N Very negative. 



H2SO4 .0002 N Still very negative. 



H2SO4 .00005 N Positive when neutral water is the other 



choice. 



The fishes used did not select alkaline water in any case except 

 when the only other choice was neutrality. Then they spent 

 most of the time on the alkaline side, rather than at the neutral 

 point. 



2. Reactions to Alkalies. 



(a) Alkalies in Neutral Water, (i) Na 2 CO s (.01 N) in Neutral 

 Water vs. Neutral Water. Six experiments were run with this 

 combination. The results were rather indefinite. However, the 

 graphs as a whole show a slight preference for the alkaline half of 

 the tank. As has been pointed out already, the fishes are nega- 

 tive to the neutral water, and these experiments confirm this 

 reaction, even though the only other choice is alkalinity. 



(b~) Alkalies in Strongly Acid Water. In this water which is 

 acid with CO 2 (18 c.c. per liter), the first action of the alkali 

 will be to neutralize the acid. Thus a small amount of alkali 

 introduced at one end will simply produce an acid gradient by 



