236 MORRIS M. WELLS. 



lessening the acidity at this end. Eighteen c.c. of CO 2 equals an 

 .0008 N solution. In most cases, the concentrations of alkali 

 used have been much greater than this and the amount used up 

 in neutralizing the acid may be looked upon as negligible. In 

 some experiments, to be cited, the acid factor is of much impor- 

 tance. 



(1) NazCOz (.01 N) in Strongly Acid Water vs. Strongly 

 Acid Water (Graph I, Chart II.}. The fishes stayed in the middle 

 of the tank, coming to the surface very little. The gradient 

 was acid at one end and alkaline at the other. Titrations showed 

 that the fishes spent most of the time on the acid side of neutrality. 



(2) NaiCOz (.002 N} in Strongly Acid Water vs. Strongly 

 Acid Water (Graph 2, Chart II.}. Fifteen experiments were run 

 with this combination. The graphs show that the fishes spent 

 most of the time nearer the alkaline end than before, but titra- 

 tion showed that they were merely following the neutral point, 

 remaining on the acid side most of the time. 



(3) Na^COz (.0005 N) in Strongly Acid Water vs. Strongly 

 Acid Water (Graph 3, Chart II.). This concentration of alkali 

 was just a little more than enough to neutralize the acid in the 

 water of the alkaline end. The end was really slightly acid, 

 however, from the diffusion of more acid from the acid end of 

 the gradient. The fishes moved into the so-called alkaline 

 (really slightly acid) end and remained there during the experi- 

 ment. This was true for all the fishes used. 



(4) NaHC0 3 (.oiN) in Strongly Acid Water vs. Strongly 

 Acid Water. This salt is neutral to phenolphthalein as has been 

 pointed out in the preceding discussion. A number of experi- 

 ments, recorded both by graphs and readings at short intervals, 

 were run with it. The results were not at all definite. The 

 fishes seemed to be indifferent to this bicarbonate in acid water, 

 or else they were not at all stimulated by its presence. 



(5) NHiOH in Moderately Acid Water (Made it Faintly Alka- 

 line} vs. Moderately Acid Water (Graphs 4 and 5, Chart II.}. Ten 

 experiments with this alkali were run, to check up Shelford and 

 Alice's work ('13) with it. They say (p. 252) that the fishes 

 (Abramis) did not react to ammonia in a concentration which 

 caused them to turn on their sides after an hour or more. In 



