260 MORRIS M. WELLS 



minutes. The fishes were then taken from the large aquarium 

 and placed in pans of water, numbered 1, etc. The fish from pan 

 No. 1 was placed in the gradient and its movements graphed 

 for 15 minutes. It was removed and No. 2 was placed in the 

 gradient and graphed. This was repeated for Nos. 3 and 4. 

 A trace of NaNOs was now added to the inflow at the salt end; 

 after 20 minutes fish No. 1 was again placed in the gradient and 

 its movements graphed for 15 minutes. This was repeated 

 for the three remaining fishes in the same order as before. The 

 graphs show the marked difference in the reactions of the fishes 

 before and after the trace of sodium nitrate was added. 



C. PHYSIOLOGICAL STATES AND THE REACTIONS OF FISHES 



In the discussion so far attention has been called to the fact 

 that in most of the series of experiments, there was a small 

 percentage of the fishes (usually 3-5 per cent) which gave re- 

 actions more or less the reverse of those given by the majority. 

 Such exceptions to the general behavior are common in experi- 

 mental work of all sorts and probably indicate physiological 

 differences upon the part of the organisms. That such physio- 

 logical differences, i.e., physiological states, exist and that they 

 influence very markedly the reactions of the animals has been 

 proven beyond doubt (Child '13, and Allee '12). Allee and 

 Tashiro ('14) have shown that the reactions of isopods are very 

 closely correlated with the metabolic activity and Allee ('12) 

 has shown that by changing the rate of metabolism he can alter 

 and even reverse the reaction of isopods to current. A correla- 

 tion between the rate of metabolism and the reactions of amphi- 

 pods has been shown by Phipps ('15). 



At Chicago during the winter of 1913-1914, a study not yet 

 published was being made of the effect of starvation upon the 

 resistance of fishes to KCN and low oxygen; it was thought that 

 the starving fishes furnished good material for ascertaining dur- 

 ing the same period something of the effects of starvation upon 

 the reactions of fishes in gradients. Accordingly a series of 89 

 experiments was run with the starving fishes in gradients; 50 



