THE BEHAVIOR OF INFUSORIA; PARAMECIUM 



85 



the upper hand, and the animal swims backward toward the anode. 

 The cilia are now reversed even behind the middle (Fig. 61, 4, 5). The 

 body is deformed, becoming short and thick, and pinched to a point at 

 the anode end, while the cathode end is swollen. Finally the animal 

 usually bursts and goes to 

 pieces ; before this happens 

 almost all the cilia have 

 become reversed (Fig. 

 61, 6). 



When a Paramecium 

 is transverse or oblique to 

 the direction of a current 

 at the time the circuit is 

 closed (Fig. 63, c, e), cer- 

 tain striking effects are 

 produced. If a current of 



medium strength is em- 

 ployed, such as causes re- 

 versal of about half the 

 cilia, the following results 

 are observed. On the 

 anode side the cilia strike 

 backward, as usual. On 

 the cathode side the cilia 

 strike forward. As a re- 

 sult the animal, when in a 

 transverse position, must 

 turn directly toward the 

 cathode side, 

 both sides of the body 



tending to produce this effect, as indicated by the 

 c and e. This happens even when the oral side is directed toward the 

 cathode (Fig. 63, e). The animal then turns toward the oral side, — 

 a result never produced by other stimuli, and due to the peculiar 

 cathodic effect of the current. 



This tendency to turn directly toward the cathodic side is compli- 

 cated in certain positions of the animal by the usual strong tendency to 

 turn, under the influence of stimuli, toward the aboral side, — that is, 

 to respond by the typical avoiding reaction. If the anterior end is 

 directed toward the anode at the time the circuit is closed, the animal in- 

 variably turns toward its aboral side, the cilia taking the position shown 

 in Fig. 63, b. This method of turning is apparently due to the fact that 



Fig. 62. — Water currents produced by the cilia in the 



electric current, a, Electric currents weak; water currents 



reversed only at cathodic tip. b, Electric currents stronger; 



the cilia of water currents reversed over cathodic half as far back as 



the middle. 



arrows in Fig. 63, 



