Jennings, Behavior of Paraviecium. 485 



tion to the electric current is in many ciliates more complex and 

 less schematic than had been supposed. As first brought out 

 in the paper of Pearl (1900), there seems to be an attempt by 

 the animal to react in the same way to the electric current as 

 to other stimuli (Pearl's "reflex factor"), but this is modified 

 or masked by certain effects peculiar to the current (Pearl's 

 "forced movements"). Cilia of different parts of the body un- 

 der the influence of the current thus differ in their method of 

 action and force of stroke. Wallengren (/. c.) shows that 

 whether anodic, kathodic or transverse electrotaxis is produced 

 depends upon the peculiar action of the cilia of certain regions 

 of the body. Thus the "action system" of the organisms does 

 play a part in determining the reaction to the electric current, 

 though not so exclusive a part as in the reactions to the stimuli 

 met under natural conditions of life. The corresponding rela- 

 tions haVe never been brought out for Paramecium ;^ this I shall 

 try to do in the following. 



Pearl (1900) confirmed Ludloff's schematic account of 

 Paramecium, though at the same time he showed, as noted 

 above, that in certain other ciliates the "action system" (his 

 "reflex factor") does play an important part in determining the 

 reaction to the electric current. Though the results of Lud- 

 loff and Pearl on Paramecium are correct so far as they go, 

 they are incomplete. The "action system" does in reality play 

 a much larger part in determining the reactions to the electric 

 current than would appear from the accounts of the two authors 

 named. This is most clearly seen in the fact that when the an- 

 terior end is directed toward the anode at the moment the cur- 

 rent is made (Fig. 14, b) the animal always reaches the position 

 of orientation with the anterior end to the cathode by turn- 

 ing toward the aboral side, as in the reactions to other stimuli. 

 Under these conditions the cilia of both the oral and aboral sides 

 beat backward in the anterior half of the body (Fig. 14, b)\ since 

 the cilia of the oral groove are more powerful than the opposing 



^ It is somewhat peculiar that these relations are not dealt with in the recent 

 extensive and valuable paper of Statkewitsch {1903, a). 



