10 VICTOR E. SHELFORD AND W. C. ALLEE 



Chart II 



Showing modification by contact with boiled water, with boiled water plus 

 oxygen to balance that of the tap water, and with tap water plus carbon dioxide. 

 For further explanation see Chart I. In experiment 78, Hybopsis did not react 

 to the effect of boiling with the oxygen factor eliminated but did react to the boiled 

 water. At the end of about two minutes after all the fishes had tried the boiled 

 water several times, the turnings in the gradient began, and the same type of modi- 

 fication was again shown (see Chart I). Ambloplites reacted to both the boiled 

 water and the boiled water with oxygen added. Detailed study of these fishes 

 from the side in the boiled water while in glass boxes showed that the respiratory 

 movement was increased but that other activity was depressed, this species being 

 an exception in the matter of depression. However, in both parts of experiment 

 83, after the fishes had tried the water in both ends several times they began to turn 

 back and make shorter stays in the modified water. 



Experiment 53 shows the reaction where sufficiently high concentration of carbon 

 dioxide was used to produce death in less than an hour. Under these conditions 

 the fishes did not turn back until two had tried the high concentration. The third 

 fish turned with the other two without entering the high concentration, a thing 

 which takes place normally in a gregarious species and thus can hardly constitute 

 a real exception. The graph is typical of the whole series of experiments until 

 the end of eight minutes when the movements become erratic due to the effect 

 of the carbon dioxide upon the fishes. In a later experiment with only a slightly 

 larger amount of carbon dioxide the fishes ceased to react properly after a short 

 time and turned upon their backs. 



