From the Rudolph Spreckels Physiological Laboratory of the University of California. 



THE MECHANISM OF THE GALVANOTROPIC 

 ORIENTATION IN VOLVOX 



FRANK W. BANCROFT 



In a recent paper O. P. Terry ('06) has recorded the discovery 

 that "if kept in the dark for two or three days, the [galvanotropic] 

 response of volvox is changed from cathodicto anodic. This may 

 then be reversed at will by exposure to light." He did not, how- 

 ever, attempt to determine the mechanism by means of which this 

 change in the direction of migration of the organism is brought 

 about. As it appeared to me that the best opportunity for study- 

 ing the nature of galvanic stimulation by the electric current was 

 presented in those cases where a reversal of the galvanotropism 

 was possible, I have investigated the effect of the current upon the 

 flagella of volvox. 



The only observation that I know of on the response of the 

 flagella of this plant to the constant current is by Carlgren ('00, 

 p. 57), who was investigating volvox that was typically swimming 

 toward the cathode. He added carmine to the fluid containing 

 the organisms, and says that on several occasions he saw the cur- 

 rent produced by the flagella stop at the anode while it continued 

 at the cathode. 



METHOD 



The 1 10 volt power current was led through a water rheostat, 

 milliammeter, pole changer and non-polarizable boot electrodes 

 to the preparation containing the volvox. The colonies were usu- 

 ally examined in a small glass and parafl5ne trough. When the 

 currents produced by the flagella were to be observed, india ink 



The Journal of Experimental Zoology, vol. iv, no. i. 



