248 MORRIS M. WELLS 



IV. PRESENTATION OF DATA 

 A. REACTION EXPERIMENTS 



I. Reaction to chlorides 



The fishes used are less sensitive to the chlorides of the salts 

 than they are to the nitrates and sulphates. They also react 

 differently in the presence of different chlorides. Thus they 

 are sensitive to both the anions and the kations, and to different 

 degrees. 



a. Ammonium chloride. The fishes were decidedly negative to 

 this salt in 0.01 N concentration. The experiments were run in 

 water that was a mixture of half aerated and half unaerated 

 tap water (i.e., moderately acid with CO2). It has been found 

 (Wells '15 a) that fishes give normal reactions in this water. 



b. Potassium chloride. These experiments were also performed 

 in water which was somewhat acid. The reaction of the fishes 

 was rather peculiar in that they were positive to a higher con- 

 centration of this salt than was expected. Twenty-one experi- 

 ments were performed and all showed this phenomenon. In a 

 number of cases the fishes selected the highest concentration for 

 a large part of the time. It was thought that the reaction might 

 be due to the positiveness of the fishes for the chlorine ion, as 

 will come out in other experiments; the known toxicity of the 

 potassium ion, however, made this conclusion seem doubtful. 

 Again, the fishes had been in the laboratory for over a month 

 and were somewhat starved. It .had already been determined 

 that starvation increases the positiveness of some fishes to cer- 

 tain salts, and thus the reaction might be laid to this. How- 

 ever, the real explanation was later found to lie in a mutual 

 antagonism which exists between certain salts and acids. Thus 

 the reaction of the fishes in selecting the salt end was a reaction 

 which brought them into the lesser stimulating part of the 

 gradient. In the tap water end, the CO2 made the water quite 

 acid. In the salt end this action of the acid was neutralized by 

 the presence of the salt and vice versa. This phenomenon was 

 noted in a number of the gradient experiments, while its cause 

 was definitely proved in the resistance experiments. 



