54 The Animal Mind 



in that direction. The cause of this has been the subject of 

 some dispute, which we shall discuss in a later chapter; but 

 the response to gravity seems in any case not to involve a new 

 form of reaction. Further, Paramecium reacts to the cen- 

 trifugal force produced by whirling a horizontal tube around 

 a vertical axis just as it does to gravity ; that is, it orients itself 

 in such a way as to swim toward the axis, in the opposite 

 direction to the pull of the force (211, p. 78). 



To an electric current the response of Paramecium is 

 more complicated. When the current is weak the animals 

 move toward the cathode. This appears to be caused simply 

 by the giving of the negative reaction so long as the front end 

 of the animal is turned toward the anode, and is thus being 

 stimulated. But if the current is made gradually stronger, 

 the movement toward the cathode grows slower and finally 

 stops. Further increase in the intensity of the current causes 

 the animal to swim backward toward the anode, and finally 

 to burst into pieces. This reversal of movement Jennings 

 has found to be due to the fact that the cilia nearest the cathode 

 have their direction reversed ; as the current is made stronger, 

 this effect is increased, until finally it balances and prevails 

 over the beat of the forward cilia (21 1, pp. 82 ff.). The animal's 

 movements are thus really discoordinated by the action of 

 the strong current. The effect seems a pathological one, and 

 probably need not be taken into account in considering the 

 normal life of the infusorian; as Jennings says, "The re- 

 action to electricity is purely a laboratory product" (211, 



p. 168). 



ii. The Mind of Paramecium 



If we now compare the behavior of Paramecium with that 

 of Amoeba in order to draw conclusions with regard to the 

 possible consciousness of the former, we find that although the 

 mechanism of reaction is decidedly more complicated in Para- 



