HELIOTROPISM IN EUGLENA 



413 



at right angles to the current lines were observed, and the current 

 made when the dorsal side was towards the anode. No change 

 was seen until the revolution on the long axis brought the dorsal 

 side towards the cathode when a more vigorous motion of the 

 particles around the flagellum could be seen, and at the same time 

 a small abrupt turn towards the cathode (fig. 5). It took four 

 or five of these turns to cause complete orientation. When the 

 organism was nearly oriented each jerk of the flagellum seemed to 



-f- 



-h 



+ 



Fig. 5 Behavior of cathodally galvanotropic Euglenae in glavanic current. 

 + = anode; — = cathode; a = dorsal surface towards cathode — slight stimulation 

 of flagellum accompanied by stronger swerving towards the dorsal side; b = cjor- 

 sal surface towards anode — no stimulation; c = anterior end towards cathode — 

 no stimulation ; d = anterior end towards anode — strong stimulation. 



cause less turning than when it was at right angles to the current 

 lines. When the dorsal side was towards the anode the organism 

 still swerved a little towards the dorsal side, but not so strongly 

 as when this side was towards the cathode. It is evident from 

 this account that the details of the galvanotropic orientation are 

 identical with the heliotropic orientation as described by Mast, 

 and which I can confirm. Euglena has no more direct way of 

 orienting than that employed in heliotropism. Jennings's con- 



