FORMATION OF ANIMAL AGGREGATIONS 



41 



ployed, such as causes reversal of about half the cilia, the following 

 results may be observed. On the anode side the cilia strike back- 

 ward as usual. On the cathode side the cilia strike forward. As a 

 result the animal, when in a transverse position, must turn directly 

 toward the cathode side, the cilia of both sides of the body tending 



~^ 



4- 



Fig. 2. — Effects of electric current on the cilia of Paramecia and the direction of 

 turning in different positions (large arrows). The small internal arrows show the direc- 

 tion in which the cilia of the corresponding quarter of the animal tend to turn the 

 animal. At/ the impulse to turn is equal in both directions and there is no result until 

 the revolution on the long axis brings the aboral side to the cathode. (From Jennings, 

 Behavior of Lower Organisms; courtesy of the Columbia Press.) 



to produce this effect, as indicated by the arrows in Figure 2. This 

 happens even when the oral side is directed toward the cathode 

 (Figure 2e). The animal turns toward the oral side — a result never 

 produced by other stimuli, and due to the peculiar cathodic effect of 

 the current." 



