394 FRANK W. BANCROFT 



different manner. The organisms do not turn as directly as possible into 

 the oriented position. They reach the position of orientation by a com- 

 plex spiral course, always turning towards the aboral side, never toward 

 the opposite side. Yet it is not impossible for them to turn toward the 

 opposite side, for in galvanotropism they do so. 



In another place ('08, p. 706) Jennings says, '* Since Euglena 

 itself has not been shown to react to electricity we cannot make 

 the comparison here." 



We shall see, however, that by the proper procedure Euglena 

 may be made to react to electricity; and that under these circum- 

 stances it always turns towards the dorsal side just as in the 

 heliotropic orientation. 



3. METHODS AND MATERIALS 



The only species studied was Euglena viridis. Both material 

 and specific diagnosis I owe to the kindness of Prof. G. N. Cal- 

 kins of Columbia University, to whom I wish to express my most 

 sincere thanks. 



This material was cultivated in many of the different media 

 described by Zumstein ('00), but the cultures most used were: 



Culture A. Boiled timothy hay infusion which did not develop 

 a putrefactive odor, but during the experiments always had a 

 pleasant aroma, and was slightly acid to litmus paper. Kept in 

 medium light. Euglenae taken from this culture were, unless 

 specially treated, always negatively heliotropic to any intensity 

 of light to which they responded at all. 



Culture B. About 20 dried yel'ow peas boiled for several hours 

 in one liter tap water. Citric acid added to make the whole de- 

 coction about 5^0 . Kept in strong light. In about two weeks 

 the whole fluid was dark green with Euglenae which were always 

 positively heliotropic to weak and negative to strong light. 



Other decoctions of both hay and peas in which the initial 

 concentration of citric acid was as high as ylo^ and f^ also gave 

 good results, especially with galvanotropism. 



The only treatment of the organisms that was attempted in 

 order to show more clearly the various phenomena studied was 

 dilution of the- culture medium with tap water, and subjection to 



