MOTOR RESPONSES 331 



occur on the anodal side. The ion movement in photoneutral colonies 

 would result in increase in positive ions, and increase in potential and 

 decrease in permeability on the cathodal side. On the anodal side there 

 would be equivalent increase in negative ions and increase in potential 

 and decrease in permeability. After the current is broken, the change 

 in distribution of ions, and its effect, would be precisely opposite in all 

 respects (Fig. 99). 



If the decrease in flagellar activity is due to local decrease in polariza- 

 tion and increase in permeability, it accounts for the observed direction 

 of movement of photopositive and photonegative colonies in a direct 

 current. And if the decrease in flagellar activity is correlated with rate 

 of change in these characteristics, it also accounts. for the fact that the 

 decreased activity induced by making or breaking the current continues 

 only a few seconds, for the change in polarization and permeability 

 undoubtedly lasts but a few seconds. 



How does the fact that strong currents cause decrease in the activity 

 of the flagella simultaneously on all sides of the colonies, harmonize with 

 this view? 



It is well known that a galvanic current will produce cytolysis if it is 

 strong enough, and that cytolysis is associated with increase in perme- 

 ability and decrease in polarization. It is therefore not difficult to see 

 that such a current could cause decrease in polarization simultaneously 

 on all sides. 



It is probable, however, that the processes involved in galvanic stimula- 

 tion, resulting in orientation, are not the same in all organisms. For 

 example, Ludloff (1895) and Statkewitsch (1903) found that in a 

 galvanic current the fluid in the body of Paramecium is carried endosmoti- 

 cally toward the surface, on which the stroke of the cilia reverses, i.e., 

 in the specimens which swim forward toward the cathode, there is, if 

 the current is strong enough, contraction at the anode and expansion 

 at the cathode end. In Volvox precisely the opposite obtains. In the one, 

 stimulation appears to be associated with increase, in the other, with de- 

 crease in water content. In both, however, as pointed out above, it ap- 

 pears to be associated with decrease in polarization. 



In general, it may be said that a galvanic current usually induces in 

 the lower organisms chemical and physical changes which differ at op- 



