MOTOR RESPONSES 



307 



+ 



+ 



+ 



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

 Amoeba moving toward the cathode, g, plasmagel; s, plasmasol ; /, plasmalemma ; c, 

 hyaline cap; h, hyaline layer; — , cathode; +, anode; arrows, direction of streaming. A, 

 very weak current, B, C, D, progressively stronger current. Note that in a current of 

 moderate density the hyaline cap disappears and the plasmasol extends to the plasmalemma 

 and that in stronger current the cathodal end expands and the anodal end contracts and 

 finally breaks, after which the granules in the plasmasol flow toward the anode, indi- 

 cating that they are negatively charged. If the surrounding medium is acid, the amoebae 

 do not break. (After Mast, 1931a.) 



terior end, and, finally, by disintegration beginning at the posterior end, 

 i.e., that which is directed toward the anode. 



If the anterior end of the amoeba is directed toward the anode and 

 the current is weak, there is merely a momentary retardation of stream- 

 ing at the posterior (cathodal) end. With successively stronger currents, 



