STRUCTURE OF PROTOPLASM OF PARAMCECIUM. 19 



accompanies the neutralization of the alkalinity of the culture. 

 The complete reversal in the sign of the charge carried by the 

 protoplasmic particles is apparently too fundamental a change to 

 occur without killing the protoplasm except under the most per- 

 fect conditions. While much more work must be done on this 

 point, we can assuredly say that the normal electrical charge 

 carried by the protoplasm of Paramcecium bears a very close 

 relation to certain chemical conditions of the environment, of 

 which the alkalinity of the surrounding medium may be taken as 

 one of the most important. These results are especially signifi- 

 cant in the light of the behavior of paramoecia from various cul- 

 tures toward different forms of stimuli, as we shall see when we 

 discuss this subject. 



III. Reactions of the Protoplasm of Paramcccuun to the Electrical 



Current. 



The above conclusions relating to the ultimate physical struc- 

 ture of protoplasm and the electrical conditions underlying it, 

 are further borne out by a study of the effects produced on the 

 structure of the protoplasm by the constant current. It has long 

 been known that the constant current has a profound polar effect 

 on the protoplasm of various protozoa. 



Thus Kiihne, Verworn 1 and others have shown that when a 

 protozoan is exposed to the action of a weak current, a contrac- 

 tion occurs on the anodal side of the cell, and a relaxation on 

 the cathodal side. This phenomenon was first described for 

 Actinospkcerium, a large heliozoan with many radiating pseudo- 

 podia. Very soon after exposure to the current the pseudo- 

 podia on the anodal side become contracted into irregular shapes, 

 and are finally completely withdrawn into the cell, while those 

 on the cathodal side remain fully extended. Amccba is still more 

 sensitive to the current. The whole cell contracts on the anodal 

 side while pseudopodia are rapidly thrown out toward the cathode 

 so that the animal moves in this direction. The same general 

 changes have been observed in Paramcecium 2 and many other 

 protozoa. If the organisms are exposed to the current for a 



1 Verworn, Arch. f. d. ges. PhysioL, 1889, XLV., p. I. 

 2 Pearl, Amer. Jour, of Physiol., 1900, IV., p. 96. 



