The Reactions of Plauarians to Light 



109 



first to come to rest and those least affected by fatigue continue 

 longest in motion 



TABLE XXIII 



The average generic and specific di^erence in fatigue 



Responses to Changes in Intensity. When worms in non-direc- 

 tive light pass from a given intensity to one 2h times as great, 

 decided differences appear in their behavior, the generic differences 

 being plainly of wider range than the specific. 



TABLE XXIV 



Average di^erences in response at the critical line separating tzvo areas of non-directive light of which 

 one {82.^0 cm.) is approximately 2\ times as great as the other {S3-^^ cm.) 



In this table Dendrocoelum is shown to respond in only 17 per 

 cent of its passages across the critical line separating the two dif- 

 ferent intensities of light, while Phagocata responds in ^"j per cent 



