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MOTOR RESPONSES 



to the solution, the organisms will swim forward toward the anode. He 

 maintains that this is due to stimulation at the anodal surface, and that 

 consequently it is an exception to Pfliiger's law. 



It is well known that some salts cause paramecia to swim backward, 



Figure 115. Progressive cathodic reversal of the cilia and change of form in Para- 

 inecium as the constant electric current is made stronger. The cathode is supposed to lie 

 at the upper end. The current is weakest at 1, where only a few cilia are reversed; 2-6, 

 successive changes as the current is gradually increased. (After Statkewitsch, 903.) 



owing to the forward stroke of all the cilia (Jennings, 1899; Mast and 

 Nadler, 1926; Oliphant, 1938). Obviously, if under such conditions 

 there is reversal in the direction of the stroke at the cathodal surface, 

 the paramecia will turn and swim forward toward the anode (Mast, 



