152 



BEHAVIOR OF THE LOWER ORGANISMS 



less affected when the aboral side is directed toward the anode, than in 

 the opposite position. 



B. Reaction to the Constant Current 



Under the action of the constant current there are a few infusoria 

 which do not react at all, so far as known. This is the case, for example, 

 with Euglena viridis. Even with powerful currents it shows no reaction. 



The larger number of free cihate infusoria swim under the influence 

 of the constant current to the cathode, while a few swim to the anode 

 or take a transverse position. A considerable number of flagellates 

 swim to the anode, though some swim to the cathode. 



The reaction of the flagellates has been httle studied in any precise 

 way. Owing to their minuteness it is usually very difficult to deter- 

 mine their exact movements. According to Verwom (1889 b), Trache- 

 lomonas and Peridinium swim to the cathode; Polytomella uvella, 

 Cryptomonas ovata, and Chilomonas Paramecium to the anode. In 

 stronger currents some of the individuals of Chilomonas swim to the 

 cathode. The reason for the diversity in the reactions of different 

 flagellates has not been determined. In the case of Trachelomonas, 

 according to Verwom, the flagellum is strongly stimulated when directed 

 toward the anode. The result is that it strikes strongly in such a way 

 as to turn the organism around, — doubtless by a typical avoiding 

 reaction similar to that described on page in for Chilomonas. On 

 reaching a position with anterior end directed to the cathode, it is no 

 longer effectively stimulated ; it therefore continues to move toward the 

 cathode. In Chilomonas the orientation to the electric current is known 

 to be brought about through the typical avoiding reaction. That is, 

 the animal turns toward the smaller lip (Fig. 72, y), till orientation is 

 attained (Pearl, 1900). Since in the flagellates the motor organs are all 

 at one end, all bear the same relation to cathode or anode, so that we 

 cannot expect any opposition in the action of the different flagella, such 

 as we find in the cilia of different regions in Paramecium. There is 

 thus no sign in the fiagellates of that lack of coordination or of an 

 apparent attempt to move in two directions at once, which we find in 

 Paramecium. 



Among the CiKata, most species, under usual conditions, turn the 

 anterior end to the cathode and move toward that electrode. But 

 Opalina moves, usually, to the anode, and Spirostomum as a rule takes 

 a transverse position. Certain variations in the reactions under different 

 conditions will be brought out later. 



Among the organisms which pass to the cathode, the manner in which 



