In preliminary tests, at the rate of four per day, the colored cardboards were placed only at the entrances to the boxes, not inside, and as was true also in the case of brightness tests under like conditions, no evidence of discrimination was obtained from ten days' training. This seemed to indicate that a considerable area of the colored surface should be exposed to the mouse's view, if discrimination were to be made reasonably easy. This conclusion was supported by the results of other preliminary experiments in which rectangular pieces of colored papers[1] 6 by 3 cm., were placed on the floor at the entrances to the electric-boxes, instead of on the walls of the boxes. Mouse No. 2 was given five series of ten tests each with a yellow card to indicate the right box and a red card at the entrance to the wrong box. At first he chose the red almost uniformly, and at no time during these fifty tests did he exhibit ability to choose the right box by color discrimination. I present the results of these series in Table 16, because they indicate a fact to which I shall have to refer repeatedly later, namely, that the brightness values of different portions of the spectrum are not the same for the dancer as for us. Previous to this yellow-red training, No. 2, as a result of ten days of white-black training (two tests per day), had partially learned to go to the brighter of the two electric-boxes. It is possible therefore that the choice of the box in the case of these color experiments was in reality the choice of what appeared to the mouse to be the brighter box. If this were not true, how are the results of Table 16 to be accounted for? [Footnote 1: These were the only Hering papers used in my experiments.] TABLE 16 YELLOW-RED TESTS In Color Discrimination Box with 6 by 3 cm. Pieces of Hering Papers at Entrances to Boxes No. 2 SERIES DATE RIGHT WRONG 1906 (Yellow) (Red) 1 Jan. 16 1 9 2 17 3 7 3 18 4 6 4 19 5 5 5 20 5 5 Without further mention of the many experiments which were necessary for the perfecting of this method of testing color vision, I may at once present the final results of the tests which were made with reflected light. These tests were made with the discrimination apparatus in essentially the same way as were the brightness discrimination tests of Chapter VII.