(iUANTITATIVE DETERMINATION OF LIGHT REACTIONS 249 



gence of 46 larvae. Thirty-four emerged on the semi-circle toward 

 the blue, and twelve on that toward the green. The trails above 

 the horizontal (90°) diameter were made by turnings to the left, 

 those below by turnings toward the right. If these trails had 

 been measured in degrees of deflection from the vertical diameter, 



Orrrn 



Fig. 17 A diagram to show the deflection of the blowfly larvae when sub- 

 jected to opposed green and blue lights of equal intensities; after Gross, slightly 

 modified. The numbers around the circle indicate the number of larvae that 

 emerged through a sector. The heavy radii A and A' indicate the average angu- 

 lar deflection as approximately computed from the data presented by Gross. 



the results would have been directly comparable to those pre- 

 sented in this paper for white lights. This deflection may, how- 

 ever, be approximately computed from the data of figure 17, by 

 giving each trail the mean angular value of the sector in which 

 it emerged from the circle. The trails to the left of the vertical 

 diameter would be measured as minus, and those to the right as 



