1 June 1 Blue 74 c.m. Green 36 c.m. 3 7 3 7 2 2 Same 5 5 4 6 3 3 Same 5 5 6 4 4 4 Same 6 4 3 7 5 5 Same 6 4 5 5 6 6 Blue 21 c.m. Green 21 c.m. 6 4 7 3 7 7 Same 2 8 3 7 8 8 Same 5 5 4 6 9 9 Same 3 7 6 4 10 10 Same 2 8 4 6 11 12 Same 6 4 3 7 12 13 Blue 36 c.m. Green 21 c.m. 3 7 4 6 13 14 Same 5 5 14 15 Blue 62 c.m. Green 21 c.m. 4 6 15 16 Same 5 5 16 17 Same 5 5 17 18 Same 6 4 Now, as a final test, blue and green glasses were placed over the electric-boxes, the brightness of the two was equalized for the human eye, and the tests of series 18 and 19 were given to No. 2:-- TABLE 27--CONTINUED NO. 2 SERIES DATE BRIGHTNESS VALUES RIGHT WRONG (Blue) (Green) 18 18 Blue 62 c.m. Green 21 c.m 4 6 19 19 Same 6 4 20 20 Blue 21 c.m. Green 88 c.m. 2 8 The green was now made much the brighter. 21 21 Blue 21 c.m. Green 18 c.m. 7 3 22 23 Same 8 2 To begin with, the blue and the green were made quite bright for the human subject, blue 74 candle meters, green 36. Later the brightness of both was first decreased, then increased, in order to ascertain whether discrimination was conditioned by the absolute strength of illumination. No evidence of discrimination was obtained with any of the several conditions of illumination in seventeen series of ten tests each. On the supposition that the animals were blinded by the brightness of the light which had been used in some of the tests, similar tests were made with weaker light. The results were the same. I am therefore convinced that the animals did justice to their visual ability in these experiments.