RESPONSE TO STIMULUS OF LIGHT 



411 



plified by specimens which are not very fresh. The sequence 

 is here ( + . . . ). In some instances, if the stimulus be stopped 

 at the end of the first negative phase, we obtain a small 

 increment of negativity as the after-effect. The sequence 

 here, then, is ( ...). 



FIG. 244. Photographic Record of Phasic Alternations, showing Direct 

 and After Effects of Light in Type I., represented by Bryophyllum 



a: First record of the series. Positive after-effect represented by dotted 

 curve is here strong, b and c : Less strong positive after-effects due to 

 fatigue. In c light was stopped slightly beyond the second phase of 

 maximum positivity; d, owing to fatigue, after-effect converted into 

 negative. Dotted portions of curve represent, as usual, the after-effect 

 on cessation of light. 



Turning to Type III., we take specimens whose charac- 

 teristic response to short-lived stimulus of light is by 

 gjalvanometric positivity, the multiple phases in which, under 

 its continuous action, may be expected to be in the se- 

 quence represented in figure 232, that is to say (-f - + ) 

 As the responses here are the exact opposite of those in 



