A STUDY OF COLOR VISION IN THE RING-DOVE 37 



day to day, but in general it was placed at 1 cm. for the female 

 and at 3 cm. for the male. This, of course, means that the male 

 responded to a very much weaker electric stimulus than did the 

 female, but it is probable that this indicates not so much a 

 difference in sensitiveness to the stimulus as the result of differ- 

 ence in weight, for the male bird was much heavier than the 

 female. During March it was found difficult to get satisfactory 

 responses, even when the maximum current was used, and the 

 experimenter finally hit upon the device of placing a square 

 piece of moist blotting paper before the food-box in the entrance 

 chamber. This was found to yield very satisfactory results. 

 The secondary now had to be set at 2 cm. for the female and 

 2\ for the male. The settings proved satisfactory throughout 

 the remainder of the work, and whereas previously the responses 

 to the electric stimulus had varied extremely, they subsequently 

 were very constant. 



RESULTS WITH CHROMATIC STIMULI 



Doves 3 and 4, having been trained to practically perfect 

 discrimination of a bright area from a dark area of the same 

 size, were tested for preference of spectral red and green. The 

 value of the red stimulus was 626 to 640/*/^, while that of the 

 green was 498 to 510/*/*. In energy, as measured by the selenium 

 cell, the red stood slightly above the green, but they were so 

 nearly the same that it seemed needless to attempt to equate 

 them more closely for these preliminary experiments. 



Table 5 presents in summary the results of the chromatic 

 reactions of doves 3 and 4. From this table it appears that 

 on April 21st, when given an opportunity to choose either the 

 red or the green chamber, without punishment, number 3 chose 

 the one as often as the other, whereas number 4 chose the red 

 eight times, the green twice. On April 22nd, in the absence 

 of general illumination and with a period of two minutes for 

 darkness adaptation before the series was commenced, the 

 results were entirely different, for number 3 selected the green 

 nine times out of ten, while number 4 chose it five times out of 

 ten. On the following day, the original conditions of April 21st 

 were reinstated and the responses were similar to those of that 



