132 



Herbert Eugene Psalter 



The fresh worms show more activity than the fatigued worms do. 

 Otherwise expressed, the worms have a tendency to change into 

 a lowered physiological state upon continued exposure to light. 



TABLE XXXV 



Fatigue ejects due to continuous exposure to non-directive lights forming adjacent fields of di^erent 

 intensities, as shown in the behavior of Phagocata gracilis 



It may be incidentally noted in Table XXXV that, as has already 

 been pointed out in another connection, the percentage of responses 

 is greater when the contrast between the light intensities is greater, 

 and that both fresh and fatigued worms respond oftener upon 

 going into the lesser intensity than when going into the greater 

 intensity. 



The time required for a worm placed in directive light to come 

 to rest; that is, to run the gamut from the state of normal activity 

 to that of rest, becomes gradually shorter with continuous expo- 

 sure. As fatigue increases the worm shifts down the scale of physi- 

 ological states in less time than when freshly subjected to directive 

 light. A specific case of this kind has already been described in 

 the paragraph on "duration of movement" (p. 105), where in 39 

 consecutive trials the change from normal activity to relaxation 

 was first made in 18 minutes, but the thirty-ninth time in ij 

 minutes, while the fortieth time even mechanical stimulus failed 

 to arouse the exhausted worm from the resting position. 



Effect of Previous Exposure to Dark. Worms kept several 

 hours in complete darkness make a larger percentage of re- 

 sponses to changes in their light environment than those which 

 previous to experimentation have been several hours in light. 

 Individuals removed from the stimulus of light for any consider- 



