84 



LIGHT AND THE BEHAVIOR OF ORGANISMS 



Euglenae are affected by light after they are oriented. He 

 thinks, however, that whatever such effects may be, they 

 are relatively unimportant in the process of orientation. 



^— f 



^\-~.e_,^^"~^\ 



b{ 



}a 



4^ 



L 4 



^^_ 



Fig. 12. Illustration of the devious path followed by Euglena in becoming 

 oriented when the direction of the light is reversed. From i to 2 the light comes 

 from above; at 2 it is reversed. The amount of wandering {a-h) varies in different 

 cases. After Jennings (1906, p. 137). 



Torrey (1907, pp. 317, 319) criticizes the analysis pre- 

 sented by Jennings in the following terms: " My analysis of 

 their responses, based upon the figure which Jennings him- 



