504 



ALFRED O. QROSS 



The results of the experiments with balanced monochromatic 

 lights of different colors are represented in table 13. 



In each record of table 13 where blue is compared with any 

 one of the other colors or with darkness the majority of the 

 cockroaches were oriented in a direction towards the blue. There 

 is, however, no consistent gradation in the percentages of re- 

 sponses that corresponds to the spectral position of the color 

 opposed to the blue. 



In the contrasts of green or yellow with other colors the major- 

 ity of the responses of the cockroach are negative to the green 

 and to the yellow. The percentages of the responses in these 

 cases are shown for greater convenience in comparison in table 

 14. 



TABLE 13 



Reactions of Periplaneta to pairs of monochromatic lights of equal 



intensity 



TABLE 14 



Percentages of reactions of Periplaneta to each of the four colors and to darkness 

 when compared with green and with yellow 



