254 



VICTOR E. SHELFORD AND W. C. ALLEE 



4. COMPARISON OF REACTIONS 



We have discussed the reaction of several species of fish to 

 various factors and the combination of these factors, without 

 especially considering the differences of reactions given by fishes 

 of different species or unlike age, to any one set of factors. In 

 this section we will discuss comparative aspects. 



a. Degree of reaction to the different factors 



Table 19 shows the average reactions of the controls. It 

 indicates that some of the fishes, as Ambloplites and Catostomus, 

 sometimes spent a greater part of their time in one end of the 

 control tank when the two ends were alike as far as we could 

 know. The majority of the controls show almost a balanced 

 time average, and in four of the ten species studied this is exactly 

 balanced. The number of turnings is more variable and in some 



TABLE 19 



Showing the average control responses for each species. The turnings are given in 

 percentage of the total number and a rating is given of the degree of asymmetry of 

 response or the apparent preference for one end. The ratings are obtained by 

 subtracting the percentages given for the two ends and dividing their sum by two. 

 For example, in the case of Ameiurus, 49 from 51 gives 2 and 42 from 58 gives 16. 

 Since the turnings do not agree with the time preferences they mut be considered of 

 the opposite sign. Adding ^16 and ^2 gives =>=14 which, divided by 2 gives the 

 rating as ±7. This is a numerical expression of the time spent and the turnings 

 from each end when they are considered of equal value. 



Ameiurus . . 

 Abramis. . . . 

 Hybopsis . . . 

 Ambloplites 

 Catostomus. 



Umbra 



Notropis 



Lepomis . . . 

 Etheostoma 

 Micropterus 



OP TURNINGS 





58 

 62 

 50 

 22 

 43 

 50 

 45 

 50 

 64 

 



S 03 

 O 



42 

 38 

 50 

 78 

 57 

 50 

 55 

 50 

 36 

 



=7 

 = 11 

 =0 

 = 20 

 = 6 

 -A 



= 13 



= 18 



