LAURENS: MONOCHROMATIC LIGHTS. 283 
the whole body was exposed, there were a few points of difference in 
the reactions to each. It therefore seemed worth while to test the 
reactions to balanced pairs of monochromatic lights, exposing first 
only the eyes; and secondly, only the skin. In testing the reactions 
Fic. 6.— Curves representing the percentages of movements toward yellow when 
paired with the three other lights, when the lights are received through both 
the skin and the eyes ( ); through the eyes only (----); and through 
the skin only (..... ). Wave-lengths as abscissae and percentages of movements 
as ordinates. Points marked on axis of abscissae are the positions of the wave- 
lengths of the middle band of each light. B = Blue; G = Green: R = Red; 
Y = Yellow. 
in which only the eyes served as receptors, the method and procedure 
followed were the same as those described on p. 264-266, with the 
modifications given on p. 268 and 277. 
The results of the tests are given in Table 8. Two sets of twelve 
