REACTIONS OF PLANARIA TO WATER. 



TABLE II. 



117 



REVERSAL OF REACTION INDUCED BY INCREASING THE VELOCITY OF THE CUR- 

 RENT. SUMMARY OF ALL REACTIONS IN EXPERIMENTS IN WHICH THE VELOCITY OF 

 THE CURRENT WAS INCREASED WHILE A REACTION WAS BEING GIVEN. 



Velocity Increased During a Negative Reaction. 



Velocity Increased During a Positive Reaction. 



No evidence has been obtained that a stronger rheotropic 

 stimulus will cause a negative reaction while a weaker stimulus 

 causes a positive reaction. No observations showed a sequence 

 of reactions during the diminution of the velocity of the current; 

 of negative in stronger current and positive in weaker current 

 (cf. Table I.). And second stirring of the current while the worms 

 were distributed over the bottom was never observed to reverse 

 the reaction from positive to negative. If the worms were giving 

 the positive reaction in weaker current they continued to give 

 the same reaction in stronger current, and usually with greater 

 precision of orientation (Table II.). When the reaction was 



