56 



ILLINOIS ACADEMY OF SCIENCE 



Figure 1, showing the reaction of a small (4 in.) micropterus do- 

 lomieu to a temperature gradient. The graph in the experiment 

 shows a decisive selection of the warmer end. The control is neutral. 

 Headings in control mean "Corresponding to Warm." etc. 



Ti/ne 



In 



min 



1 



2 



3 



4 



5 



6 



7 



8 



9 

 10 

 11 

 12 

 13 

 14 

 15 



16 

 17 



18 



19 



20 

 21 

 22 

 23 

 24 

 26 



Expt 



. M. C. 



3 0. 5 



Control . 



Cor. Cor. Cor 

 to to tc 



W. M. C. 



L 



J 



