258 



VASIL OBRESHKOVE 



sity and that the relation is inverse. Curve B characterizes 

 the steady rate of increase in the velocity of change in the recep- 

 tors with an increase of intensity of illumination. These graphic 

 representations and the intensity-reaction-time products furnish 

 additional evidence that the changes in the photoreceptors in 

 this animal proceed according to the Bunsen-Roscoe law. 



Lo0- of reoction-fime 



0.7 OS IJ U l£ 1.7 W 2.1 2J 



^,60 



c 

 o 



120 



O 80 





o:8 p 



o 



-J 



SvteTisity- Cavdie meters 



Fig. 4 Curve A illustrates the data in table 4. The reaction-time is plotted on 

 the ordinates, as function of intensity, plotted on the abscissa. Curve B rep- 

 resents the logarithmic relation between the reaction-time and intensity of 

 illumination of the same data. 



If, now, the curves in figure 2, illustrating the relation of the 

 intensity of illumination to the reaction-time of tadpoles with 

 eye and skin, and the curves in figure 4, giving this relation of 

 records obtained from blind tadpoles, are plotted with regard 

 to the same axis, they will be seen to coincide almost exactly. 

 This is apparent from an inspection of the data and curves, and 

 for this reason no such graphic comparison has been under- 

 taken. 



