MOVEMENTS, ETC , OF FEESH-WATEK PLANAEIANS. 689 



kathode slowly, and this process may be continued until com- 

 plete reversal is brought about and the animal comes to lie 

 again in line with the current, but with the anterior end now 

 directed towards the kathode. This reversal into the usual 

 orientation is the typical reaction for fresh specimens at the 

 first trials of the current ; it is shown in Fig. 46. In case the 

 specimens have been under the action of the current for some 

 time, there is no reversal of the position. The specimen 



+ 



+ 



J + 



Fig. 46. — Diagram showing the eleclrotactic reaction of Planaria wlien 

 the long axis of the body is in line witii the current direction, and 

 the head is towards the anode. Contracted portions are indicated 

 by heavy lines. 



simply remains in the same position and contracts strongly at 

 the anode (head) end of the body. 



Strong currents have the same effect as described in the 

 preceding experiment. Very weak currents either have no 

 definite effort, or else cause a slight jerking back of the head, 

 and turning a little to one side at the moment of making. 



After the animals have become partially paralysed by the 



