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bulletin: museum of comparative zoology. 



those in which the light with the shorter wave-lengths in each pair 

 proceeded from generator A, and those in which it proceeded from 

 generator B. In this way it was hoped to eliminate possible errors in 

 the working of the generators. However, though the results were, in 

 the main, the same as those obtained with single monochromatic 

 lights, it cannot be said that there is much evidence in favor of positive 

 phototropism for the red light. There were, for each pair of lights, 

 some movements toward both lights, with the larger percentage 

 always to the blue, or to that light of a given pair which in the spec- 



FiG. 4. — Curves representing the percentages of movements toward red when 

 paired with the three other lights, when the hghts are received through both the 



sldn 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 each light. B = Blue; G = Green; R = Red; 

 Y = Yellow. 



trum was nearer the blue. Even in the pairs in which red occurred, 

 there were movements toward this light. But, when the lights with 

 which red was paired were used singly, there were movements to the 

 dark, that is, movements away from these lights. If the results 

 obtained here are compared with those given in Table 1, and the 

 curves shown in Fig. 3 compared with those shown in Fig. 4, it will be 

 seen that the percentages of movements toward the red, when paired 



