6o 



Herbert Eugene Walter 



While the extremes of the series of definite changes indicate a 

 general rise in the percentage of their occurrence with an increase 

 of intensity, and while in the same way the extremes of the series 

 of indefinite changes suggest in general a decrease of frequency 

 with the increase of intensity, it can hardly be maintained that 

 the character of the changes in course is definitely correlated in 

 the majority of cases with changes in intensity. 



Degree of Wandering. Wandering is not closely correlated 

 with the intensities of light. In Table VII, which deals with the 

 percentage of straight paths made by P. gonocephala under dif- 

 ferent intensities of non-directive light, this fact is expressed nega- 

 tively, since it is held that a straight path is a good indication of 

 the absence of aimlessness or wandering and may thus serve as a 

 negative measure of such behavior. 



TABLE VII 



Percentage of straight paths made by P. gonocephala in the dark and also in non-directive light of different 



intensities 





o 



0.94 



II 



39 



78 



126 



'55 



217 



43 ! 







*3 



24 



34 



3 1 



19 



33 



2 5 



2 3 



35 





In this respect again the behavior of the worms under the high- 

 est intensity is more pronounced than under any other intensity 

 since the greatest number of straight paths were laid at an inten- 

 sity of 431 cm. 



Interval of Response. There seems to be some evidence that 

 the interval of time elapsing between the reception of a light stim- 

 ulus on the part of a worm and its consequent response, may be 

 quite considerable. Three facts were established that may sup- 

 port this conclusion. 



First, when two-minute records were made under various inten- 

 sities, it was found that the worms averaged a faster rate during 

 the second minute of exposure to the light than during the first, 

 in spite of the facts that the mechanical stimulus due to placing 

 the worm in the light machine had a more quickening influence 

 during the first minute and that the fatigue effects were more 

 likely to appear during the second minute. The actual figures 



