200 LIGHT AND THE BEHAVIOR OF ORGANISMS 



a condition the anterior end is simply turned sharply in the 

 direction opposite to that in which it is when it receives 

 the stimulus, just as in the case of blowfly larvae. Thus 

 it is turned toward the source of light about as often as 

 from it, regardless of the light intensity. I found this to be 

 true in direct sunlight, contrary to Harper's conclusion, as 

 well as in light of lower intensities. 



If the animal however is rather sluggish so that there is 

 little lateral movement of the anterior end it turns from the 

 source of light with very few exceptions. The direction in 

 which the anterior end started to move after exposure to 

 lateral illumination in six such specimens is recorded in 

 Table VII. These specimens were allowed to orient in light 

 of 15 ca. m. intensity, after which they were suddenly ex- 

 posed to a horizontal beam of light, ordinarily of higher 

 intensity, from one side. There was but little lateral move- 

 ment of the anterior end after the specimens were oriented 

 in the lower intensity, and they moved so slowly that the 

 direction in which the anterior end started to turn after 

 one side was illuminated could be clearly seen. 



TABLE VII 



In a few other sluggish specimens the exposure to unilat- 

 eral illumination was not made until after they had come 

 to rest in the light of 15 ca. m. Under such conditions the 

 animals did not react at all until a few moments after 



