188 



EDWIN B. POWERS. 



TABLE III. 



Showing the vigor of reaction or rating of the crayfishes in gradients of carbon 

 dioxide and acetic and hydrochloric acids. The rating is obtained by subtracting 

 the percentages given for the time preference for the two ends and subtracting 

 the percentage of turnings from the two ends and adding the two remainders 

 (which are considered of different signs since turnings are from opposite end to end 

 preferred) and dividing by two. The table also shows difference in concentration 

 between the two ends and the ratio of increase of gradient at high end over low end 

 or Weber's ratio. 



