76 CHAP. X. THE ELECTRIC RESPONSE TO LIGHT 



When the light is suddenly stopped, the A effect is often 

 found to be more persistent than the D, the result being a 

 transient overshooting of response in the positive direction. 



Fig. 19 Fig. 20 



Fig. 19. The Negative Electric Response of Musa to Light, up- 

 curve exhibiting the predominant D Reaction 



Note the unmasking of A in the positive after-effect. 



Fig. 20. The ' Overshooting ' of the Response of Musa in the 

 positive direction on the cessation of Light 



Note neutralisation under continuous light, and the unmasking 

 of the positive A on stoppage of illumination l. 



The positive after-effect has already been demonstrated by 

 means of mechanical response (p. 56). 



Electric response : positive after-effect. — In the record 

 of the electric responses of Musa to light, the up-curves 

 indicate galvanometric negativity during the continuance 



