308 



MOTOR RESPONSES 



the streaming at this end ( 1 ) stops a few moments, then begins again, 

 and continues in the original direction; (2) it stops a bit longer, then 

 begins, and continues in the reverse direction, i.e., the plasmasol then 

 streams toward the cathode at one end and toward the anode at the other 

 (Fig. 112); (3) the reversal extends to the anodal end, and a new hya- 

 line cap forms at the original posterior end, which now becomes the an- 

 terior end; (4) the reversal is followed by marked contraction at the 



-I- 



-I- 



Figure 112. Sketches illustrating the effect of a galvanic current on monopodal amoebae 

 moving toward the anode in a weak current. Labels are the same as in Figure 111. Note 

 that the direction of streaming reverses, that it begins at the cathodal end and proceeds 

 toward the anodal end, and that this results in movement in opposite directions at the 

 two ends during one phase in the process of reversal. (After Mast, 1931a.) 



anodal end, which is followed by partial or complete disintegration, al- 

 ways beginning at the anodal end. The fact should be emphasized that 

 no matter how extensive a reversal in the direction of streaming may be, 

 it always begins at the cathodal end of the amoeba. 



When the contraction at the anodal end begins, the hyaline layer in 

 this region becomes thicker here and there, resulting in the formation 

 of several small blisters and in numerous minute papilla-like foldings in 

 the plasmalemma (Fig. 111). As contraction continues, some of the 

 blisters, containing fluid and a few granules in violent Brownian move- 



