460 GERTRUDE MAREAN WHITE 



The first test was successfully accomplished by only one fish, 

 no, 27. The colored discs offered were blue as a signal that the 

 forceps held food and red to represent paper. The forceps with 

 the colored discs attached were presented singly. The duration 

 of the experiment was seventeen days (Feburary 1 1 to February 

 27). The results are shown in figure 1, B. On the first day 

 three errors were made, i.e., the fish snapped at the paper under 

 the red disc three times. On the second and third days the fish 

 refused to eat on red, but took food on the appearance of the 

 blue disc. Two mistakes were made on the fourth day, after 

 which the fish no longer attempted to obtain food on red. In 

 two instances a day intervened when the fish was not fed, in 

 one instance two consecutive days, after which intervals the fish 

 made a perfect record. 



The curves for all the experiments to be described are plotted 

 in the same way. The days of the experiments are shown in 

 the abscissa and the number of errors recorded each day on the 

 ordinate. When no mistakes were made the curve is at 0, but 

 the number of correct tests is not designated in the curves. The 

 results of all the experiments with the mudminnows and stick- 

 lebacks are summarized in tables 1 and 3, respectively, showing 

 the duration of each experiment, the total number of trials, 

 the number of errors and of correct records, and the percentage 

 of errors and of successes in each case. 



After mudminnow no. 27 had learned to distinguish between 

 the red and the blue discs, violet was substituted for the blue 

 disc. (Fig. 1, D, and table 1.) The entire experiment con- 



TABLE 1 



Results of experiments in ivhich mudminnows ivere taught to take food offered with 

 certain colored papers or with light passed through monochromatic gelatin filters, 

 and to refuse paper resembling food in appearance when offered ivith certain other 

 colored papers or other monochromatic lights. 'Lights from flashlight means that 

 the source of illumination xoas a hand electric flashlight and that the light passed 

 through a monochromatic gelatin filter before reaching the fish; 'lights dim' means 

 that the dry cell in the flashlight ran down so that the light had a low intensity. 

 'Lights' means that an incandescent electric lamp was used and that the light was 

 passed through monochromatic gelatin filters. 'Intensity varied' means that differ- 



