Immediately after the brightness series, the influence of making first one color, then the other, the brighter was studied. Throughout series 9 the brightness value of the left box remained 3 candle meters, that of the right side 1800 candle meters. Number 2 was so badly confused by this change that his mistakes in this series numbered 12; No. 5 made only 4 incorrect choices. Then series after series was given under widely differing conditions of illumination. The expression "mixed values," which occurs in Table 26 in connection with series 14 to 22 inclusive, means that the brightnesses of the green and the red boxes were changed from test to test in much the way indicated by the sample series of Table 25. In view of the results of these 22 series, 320 tests for each of two mice, it is evident that the dancer is able to discriminate visually by some other factor than brightness. What this factor is I am not prepared to say. It may be something akin to our color experience, it may be distance effect. No other possibilities occur to me. Table 26 shows that discrimination was relatively easy for Nos. 2 and 5 with green at 3 candle meters and red at 1800. That their discrimination was made on the basis of the greater brightness of the red, instead of on the basis of color, is indicated by the results of the brightness check series 8a. Increase in the brightness of the green rendered discrimination difficult for a time, but it soon improved, and by no changes in the relative brightness of the two colors was it possible to prevent correct choice. In addition to giving point to the statement that red appears darker to the dancer than to us, the above experiment shows that the animals depend upon brightness when they can, and that their ability to discriminate color differences is extremely poor, so poor indeed that it is doubtful whether their records are better than those of a totally color blind person would be under similar conditions. Surely in view of such results it is unsafe to claim that the dancer possesses color vision similar to ours. Perfectly trained as they were, by their prolonged green-red tests, to choose the green, or what in mouse experience corresponds to our green, Nos. 2 and 5 offered an excellent opportunity for further tests of blue- green discrimination. For in view of their previous training there should be no question of preference for the blue or of a tendency to depend upon brightness in the series whose results constitute Table 27. TABLE 27 BLUE-GREEN TESTS NO. 2 NO. 5 SERIES DATE BRIGHTNESS VALUES RIGHT WRONG RIGHT WRONG (BLUE) (GREEN) (BLUE) (GREEN)