464 GERTRUDE MAREAN WHITE 



Mudminnow no. 27, with which the two previous sets of ex- 

 periments with the colored discs had been successfully com- 

 pleted, learned to discriminate between red and blue lights 

 shining through monochromatic filters (red, no. 71; blue, no. 

 76) when they were presented alternately; blue representing the 

 food stimulus and red, paper. The duration of the experiment 

 was thirty-four days (July 9 to August 11). No errors were 

 made during the last ten days. Red no. 70 was substituted for 

 red no. 71 without affecting the outcome (fig. 1, C). 



Fish no. 25 (which during the winter had not given successful 

 results when the red and blue discs were presented alternately, 

 but had later learned to discriminate between them when they ap- 

 peared simultaneously) made a perfect record for ten days with 

 the lights red no. 71 and green no. 74 in a series of tests which 

 lasted thirty-six days (July 11 to August 15). The lights were 

 flashed upon the vessels alternately, red representing food and 

 green, paper. During this experiment red no. 70 and green no. 

 75 were several times substituted for the filters habitually used, 

 and the fish reacted in the same manner as it was accustomed 

 to react to red no. 71 and green no. 74. (Fig. 3, A, and table 1.) 



In both of these experiments with the gelatin filters a rather 

 interesting occurrence took place. The flashlight batteries be- 

 gan to grow dim about the thirteenth day and were not renewed 

 until the twenty-third day. During the period when the lights 

 were dim, there was a great increase in the number of errors, 

 which ceased as soon as the batteries were renewed. A sudden 

 rise in curve C, figure 1 (a-a), and curve A, figure 3 {a~a) during 

 the time when the lights were dim may be noted. 



The greatest aptitude displayed by any fish was that of mud- 

 minnow no. 40, a female ready to spawn. The colored lights 

 used were green no. 74 for food and red no. 71 to be rejected. 

 On the first day when both colors were offered, the fish made 

 three failures, attempting three times to take food in red light. 

 Forthe eleven days following this shemade correct discriminations. 

 Her behavior at the appearance of the two lights was different. 

 To green she responded by rising immediately to the surface; 

 ivhen red was flashed upon her, she swam about rather excitedly, 



