462 GERTRUDE MAREAN WHITE 



tinued seventy-five days (March 3 to May 17). During the 

 last thirty-five days (April 18 to May 17) not a single mistake 

 occurred. This period included thirteen consecutive days when 

 the fish would not eat, but the associational impression was re- 

 tained during the interval. The blue-violet combination seemed 

 a more difficult one for the fish to master than the red-blue, 

 since the time required for enough consecutive perfect records 

 to be made to show that the association was established was 

 much longer than in the previous experiment. The previously 

 formed association did not seem to be of any assistance as a 

 preparation for learning the new combination. 



Mudminnow no. 25 was also tested with the red and the blue 

 discs presented alternately under the same conditions used with 

 mudminnow no. 27, but no color association was formed. The 

 discs were then offered simultaneously to discover whether the 

 failure was due to the complexity of the test or to lack of color 

 vision. When the two discs appeared at the same time, the 

 fish learned to seek the blue first. This show^ed that while 

 the fish was able to discriminate between the red and the blue 

 papers, it did not inhibit the impulse to take food when one disc 

 was shown separately. The duration of the test was seventy- 

 nine days (March 3 to May 22.) (Fig. 1, A, and table 1.) 



These experiments are subject to the criticisn made upon the 

 work of other investigators, as the colors are not spectrally pure. 

 In any case, however, they clearly demonstrate that fishes are 

 capable of forming associations and receiving suggestions from 

 the conditions connected with obtaining their food, and that 

 these associations may persist for a considerable time. 



Experiments with monochromatic light filters attached to the end of 



a flashlight 



In order to test accurately what wave-lengths of light could 

 be discriminated by the fishes, monochromatic filters were used 

 instead of the colored papers. A set of Wratten monochromatic 

 gelatin filters was obtained from Eastman Kodak Company. 

 The set consists of seven filters, mounted between glass slides, 

 which allow light of the following waves-lengths to pass through : 



