Jennings, Behavior of Paraniechan. 505 



"the road to a direct physical explanation of electrotaxis. In 

 criticism of the views of Greeley, so far as hitherto brought 

 out, the following must be said : 



1. All thorough work thus far shows that the essential 

 point in the reaction to the electric current is the method in 

 which the current affects the cilia. No attempt has been made 

 to show how the known effects on the cilia could be produced 

 through the factors emphasized by Greeley, and it would un- 

 doubtedly be difficult or impossible to bring the two into relation. 



2. The movement toward the anode is not limited to acid 

 solutions, but is known to take place in a still ' more striking 

 way in various salt solutions, especially in a solution of sodium 

 chloride. I have observed it even in a solution of sodium bicar- 

 bonate, having of course an alkaline reaction. 



3. The movement to the anode in such solutions is back- 

 ward. It has been so described by Loeb and Budgett (1897, p. 

 532), by PiJTTEK (1900, p. 297), and so far as I am aware, by 

 every one who has described it carefully, and I can myself con- 

 firm this fact. The organisms thus become oriented in the same 

 manner, with anterior end to the cathode, as under usual con- 

 ditions. Further, these same solutions produce backward swim- 

 ming even without the use of the electric current. We have 

 then all the existing features of the reaction fully accounted for 

 without taking into consideration the factor considered essential 

 by Greeley. The electric current taken by itself accounts for 

 the orientation in the usual way ; the chemical stimulation 

 taken by itself accounts for the swimming backward ; the com- 

 bination of the two accounts for the swimming backward to 

 the anode. 



4. The swimming to the anode continues only as long as 

 the chemical stimulation exists. As soon as the organism has 

 had time to become acclimatized to the chemical, it szvims as 

 usual to the cathode. This has been shown by Putter (1900), 

 and by Statkewitsch (1903 a), and I can confirm it. Often it is 

 but a few moments that the swimming backward to the anode 

 continues. 



In view of all these facts, it cannot be held on the evi- 



