In all of the color experiments, unless otherwise stated, a series of ten tests each day was given, until satisfactory evidence of discrimination or proof of the lack of the ability to discriminate had been obtained. The difficulties of getting conclusive evidence in either direction will be considered in connection with the results themselves. For all of these tests with reflected light the Milton Bradley colored papers were used. These colored papers were pasted on white cardboard carriers. I shall designate, in the Bradley nomenclature, the papers used in each experiment. With colored cardboards inside the electric-boxes as well as at their entrances (see Figure 14 for position of cardboards) blue-orange tests were given to Nos. 2 and 3 until they discriminated perfectly. The papers were Bradley's blue tint No. 1 and orange. Number 2 was perfect in the twelfth series (Table 17), No 3 in the fourteenth and again in the sixteenth. They were then tested with a special brightness check series which was intended by the experimenter to reveal any dependence upon a possible brightness difference rather than upon the color difference of the boxes. TABLE 17 LIGHT BLUE-ORANGE TESTS IN COLOR DISCRIMINATION BOX SERIES DATE NO. 2 NO. 3 1906 RIGHT WRONG RIGHT WRONG (LIGHT (ORANGE) (LIGHT (ORANGE) BLUE) BLUE) 1 Jan. 26 7 3 1 9 2 27 7 3 5 5 3 28 7 3 6 4 4 29 7 3 7 3 5 30 7 3 4 6 6 31 10 0 7 3 7 Feb. 1 9 1 7 3 8 2 8 2 6 4 9 3 9 1 9 1 10 5 7 3 5 5 11 6 8 2 5 5 12 7 10 0 5 5 Special brightness check series (see Table 18) 13 8 10 0 7 3 Special light blue-dark blue series 14 9 8 2 10 0 15 10 9 1 9 1 Special light blue-dark blue series 16 11 9 1 10 0 Special brightness check series 17 12 10 0 9 1 TABLE 18 LIGHT BLUE-ORANGE Brightness check series Mouse No. 2, Series 13 Feb. 8, 1906 TEST CONDITION RIGHT WRONG