MOTOR RESPONSES 309 



ment, round up and are pinched off; and others together with the 

 plasmagel break, after which granules in the plasmasol stream out and 

 proceed rapidly toward the anode. This continues until frequently there 

 is nothing left intact except a crumpled membranous sac, the plasma- 

 lemma. The plasmagel changes entirely into plasmasol and is carried 

 away. The fact that the granules are carried toward the anode shows that 

 they are negatively charged. 



McClendon (1910) came to the same conclusion concerning the gran- 

 ules in the eggs of frogs and the cells in root tips of onions. But Heil- 

 brunn (1923) says: "Particles in the interior of living cells bear a posi- 

 tive, whereas the particles in the surface layer have a negative charge." 



If a small amount of HCl is added to the culture solution, the amoeba 

 does not disintegrate, regardless of the current strength. Its plasmagel 

 turns distinctly yellow at the anodal end immediately after contraction 

 begins, after which it increases in thickness until the entire amoeba has 

 solidified and is dead. If the current is broken before more than about 

 one-fourth of the amoeba has gelated, the gelated portion is usually 

 pinched off. The rest of the amoeba then proceeds normally. 



If the amoeba is moving toward the anode when the current is made, 

 streaming of the plasmasol reverses before it stops at the anodal end. 

 This behavior demonstrates conclusively that the effect of the current 

 begins at the surface directed toward the cathode. The fact that before 

 the reversal occurs, the thick plasmagel at the cathodal end is replaced 

 by a very thin plasmagel sheet and a hyaline cap strongly indicates that 

 the first effect of the current is solation of the plasmagel at the cathodal 

 surface. This conclusion is supported by the facts that if the anterior end 

 is directed toward the cathode when the current is made, the plasmagel 

 sheet disappears entirely, the anterior end enlarges, and the plasmasol 

 extends to the plasmalemma. It is also true that if the current passes 

 through the amoeba in a direction perpendicular to the longitudinal 

 axis, the forward streaming stops, and pseudopods are formed on the 

 cathodal side. 



The contraction of amoeba at the anodal end, and the increase in the 

 thickness of the plasmagel — especially in specimens directed toward the 

 anode — seem to show that the current causes gelation at the anodal sur- 

 face. 



The facts that the end directed toward the cathode enlarges, that the 



