328 VICTOR E. SHELFORD AND EDWIN B. POWERS. 



3 H2.S 4 



5 H fONS 6 



Chart I. 



E, experiment; C, control;/, fresh water, T, and figures following show temper- 

 ature difference. 



Graph i shows the reaction to a difference of 0.6 of a degree the lower avoided 

 temperature being on. the left. Graph 2 shows the movement of the fishes in the 

 tank when there is no difference in temperature (see also graph 6 and other graphs 

 marked C). 



Graph 3 shows the avoidance of hydrogen sulfide introduced at the right. After 

 a few trials the avoidance became very sharp. Graph 4 is the control, i. e., with 

 no difference between the ends. 



Graph 5 shows the reaction of a fish to fresh water introduced at the right 

 showing the avoidance of the acid salt water and selection of the alkaline fresh water 

 with the incline described on p. 327 in position. Temperature the same at the two 

 ends. Graph 6 is the control of the same. 



Graph 7 shows the selection of lower temperature with the incline screen cage 

 in position; difference in beginning .55° C, at end .25° C. A difference in tem- 

 perature occurred in some of the incline experiments but lower at the salt end. 

 The graph shows that the fishes would have selected the salt water end where the 

 temperature was a little lower if they had been reacting to temperature. 



