ASSOCIATION AND COLOR DISCRIMINATION 475 



Smmnary of experiments in regard to color vision of mudminnows 



1, Mudminnows are able to distinguish between the following 

 wave lengths of light: red, 600 /x to 730 /x and green 510 // to 570 /x; 

 red 600 M to 730 ^ and blue 420 m to 480 m ; yellow 580 m to 630 m, 

 660m to 710m, and green 510m to 570m, as is shown by the forma- 

 tion of associations of paper and food with these colored lights. 



2, Red and blue, and red and violet papers are distinguished 

 in the same way. 



3. Varying the relative intensities of the colored lights from 

 1.4 cm. to 4.9 cm. does not affect the result, which indicates 

 that the reaction is to color rather than to intensity. 



4. This conclusion is further supported by the fact that fishes 

 (no. 55 and no. 60) which had previously shown that they per- 

 ceived the difference between monochromatic gelatin filters 

 (mudminnow no. 55 has shown a nearly perfect record with red 

 and green, fig. 3, D) could not distinguish between photographic 

 plates which had been 'fogged' to different shades of gray. 



EXPERIMENTS WITH STICKLEBACKS 



The tests applied to the sticklebacks were similar to those 

 made upon the mudminnow. Experiments were performed using 

 the electrical apparatus attached to the rheostat previously de- 

 scribed (fig. 5). Two sets of monochromatic filters were pre- 

 sented to the fishes; these were yellow no. 73 with blue no. 76, 

 and red no. 71 with green no. 74. After repeated tests with the 

 red and green filters, the light intensity was varied, as had been 

 done with the mudminnows. Observations were also made to 

 test the discrimination of shades of gray. 



EXPLANATION OF FIGURES ON FOLDER 



Fig. 6 Curves representing the results of experiments on the discrimina- 

 tion of light shining through photographic plates 'fogged' to different shades 

 of gray. Construction of curves same as in figure 1. 



A. Mudminnow no. 55. Dark gray plate indicating presence of food and 

 lighter gray plate indicating presence of paper. Duration of the experiment, 

 30 days. May 12 to June 10. 



B. Mudminnow no. 60. Dark gray plate indicated presence of food and 

 light gray plate indicated presence of paper. Duration of the experiment, 51 

 days, April 21 to June 10. There was no day without one or more errors. 



