ORGANIC RESPONSE 



251 



ical bending of a plant and the movement of 

 flying organism, but careful experiment has 

 that it is not curiosity that 

 leads the moth to the candle, 

 nor the exercise of a choice of 

 any sort, but rather a mechani- 

 cal orientation which the insect 

 is powerless to control. Again, 

 if microorganisms, such as Para- 

 mecia, be placed in a narrow 

 trough of water through which 

 a weak current of electricity is 

 passed, they will orient them- 

 selves in the direction of the 

 current and swim to one or the 

 other of the two poles (usually 

 the negative). This action is 

 equally as unvolitional as the 

 response to the source of light 

 and may be reversed as often 

 as the direction of the current 

 is reversed. 



We know very little of the 

 nature of the mechanism under- 

 lying this phenomenon. Nor- 



a free- 

 shown 



