316 MOTOR RESPONSES 



strength of the plasmagel varies directly with its thickness, as is doubt- 

 less true, this would result in formation of pseudopods at the cathodal 

 surface. This has been confirmed by observation. Since streaming toward 

 the cathode begins at the cathodal surface before it does at the anodal 

 surface, movement toward the cathode must be due primarily to the 

 solation of the plasmagel at the cathodal surface. The accumulation of 

 positive ions at this surface therefore must produce the solation. But this 

 obviously does not account for the disintegration of the entire organism. 

 Neither does it account for the violent contraction preceding disintegra- 

 tion at the anodal side. It will be remembered that violent contraction 

 and disintegration beginning at the anodal surface were observed only 

 in relatively strong currents. Furthermore, the reactions were observed 

 to occur only after large pseudopods develop and begin to advance to- 

 ward the cathode. 



An amoeba disintegrates only if the direct current applied is suffi- 

 ciently strong. After the circuit is closed, there is, on the inner surface of 

 the plasmagel or in the plasmagel, an accumulation of positive ions at 

 the cathodal side, and of negative ions at the anodal side. The former 

 produces a decrease in the elastic strength of this layer, which results in 

 the formation of a pseudopod directed toward the cathode — a pseudopod 

 in which the plasmagel extends to the plasmalemma. Local disintegra- 

 tion occurs at first; but, as the current continues, more and more of the 

 plasmagel in this pseudopod disintegrates. The accumulation of nega- 

 tive ions and consequently of hydrogen ions at the anodal end causes a 

 thickening of the plasmagel, as well as gelation of the adjoining plas- 

 masol. This results in violent contraction and finally in the rupture ob- 

 served at the anodal end. 



Cataphoresis and electroendosmosis are probably also involved. The 

 granules in Amoeba are negatively charged in relation to the fluid. The 

 fluid consequently tends to flow from the anodal toward the cathodal 

 end. This would facilitate contraction at the former and expansion at the 

 latter end, which is precisely what was observed. There is, however, some 

 evidence to indicate that transfer of water is of little importance in the 

 rupture and disintegration at the anodal end. This will be presented later. 



It is therefore fairly clear how, in a direct current, substances accumu- 

 late locally; and how this can produce most of the processes associated 

 with the responses of amoebae in it. But in an alternating current the 



