CHAPTER IX 

 REACTIONS OF INFUSORIA TO THE ELECTRIC CURRENT 



i. DIVERSE REACTIONS OF DIFFERENT SPECIES OF INFUSORIA 



THERE is great diversity in the gross features of the behavior of differ- 

 ent infusoria under the action of the continuous electric current. Some 

 swim, like Paramecium, to the cathode ; some to the anode ; some take 

 a transverse position ; some swim to one electrode in a weak current, 

 to the other in a strong current ; some, finally, do not react at all. Yet, 

 in spite of this great diversity, we find the fundamental effect of the 

 current on the motor organs to be almost identically the same through- 

 out the series. In all infusoria having cilia in different regions of the 

 body, the cilia of the cathode region strike forward, those of the anode 

 region backward, just as we have seen to be the case in Paramecium. 

 How the organisms move under these conditions depends on the pecu- 

 liarities of structure and of the action system of the infusorian in ques- 

 tion. We shall review here the different types of behavior under the 

 action of electricity, endeavoring to show how each is brought about. 



A. Reaction to Induction Shocks 



We may again take up, first, the reactions to single induction shocks, 

 studied by Roesle (1902) and Statkewitsch (1903). In all infusoria 

 investigated the reaction to moderately strong induction shocks is es- 

 sentially similar to the reaction to other stimuli. The animal usually 

 responds to the shock by the avoiding reaction, which begins with a 

 reversal of the cilia in that part of the body directed toward the anode. 

 In some cases, however, the induction shock causes, like a weak mechani- 

 cal stimulus, a mere movement forward (Roesle, 1902). If the shock 

 is a powerful one, the body may contract in the anode region, or, in the 

 case of very contractile species, such as Lacrymaria and Spirostomum, 

 the entire body may contract. Reaction takes place most readily as a 

 rule when the sensitive anterior end is directed toward the anode, or 

 especially, according to Roesle, when the mouth opening is precisely 

 directed toward the anode. When the animal is in the transverse posi- 

 tion, it is least affected by the induction shock, and in many cases it is 



