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 



Fig. 6. — Curves repre.senting 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 ( ) ; tlirough the eyes only ( ) ; and tlirough 



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 eacli 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 



