Galvanotropic Orientation in Volvox 163 



The fact that nothing of the nature of a motor reflex or reversal 

 in the direction of the effective stroke of the flagella has been 

 observed makes it very probable that, as indicated by Holmes, 

 the heliotropic orientation is also brought about by differences in 

 the strength of the stroke on the sides tow^ard and away from the 

 light. It would seem then that in the case of the orientation of 

 volvox to light we have also a tropism pure and simple without 

 any indication of orientation by trial and error. 



LITERATURE CITED 



Bancroft, F. W., '05 — Ueber die Giiltigkeit des Pfliigerschen Gesetzes fiir die 

 galvanotropischen Reaktionen von Paramecium. Pfliiger's Archiv, 

 vol. 107, pp. 535-556- 

 '06 — The Control of Galvanotropism in Paramecium by Chemical Sub- 

 stances. Univ. of Cal. Pub., Physiol., vol. 3, pp. 21-31. 

 '06a — On the Influence of the Relative Concentration of Calcium Ions 

 on the Reversal of the Polar Effects of the Galvanic Current in 

 Paramecium. Jour. Physiol., vol. xxxiv, no. 6, pp. 444-463. 



Carlgren, O., '00 — Ueber die Einwirkung des constanten galvanischen Stromes 

 auf niedere Organismen. Engelmann's Archiv, 1900, pp. 49-73. 



Holmes, S. J., '03 — Phototaxis in Volvox. Biol. Bull., vol. 4, pp. 319-326. 



LoEB, J., '05 — On the Changes in the Nerve and Muscle which seem to Underlie 

 the Electrotonic Effects of the Galvanic Current. Univ. of Cal. Pub. 

 Physiol., vol. 3, no. 2, pp. 9-15. 



Terry, O. P., '06 — Galvanotropism of Volvox. Amer. Jour. Physiol., vol. xv, 

 pp. 235-243. 



Wallengren, H., '02 — Zur Kenntniss der Galvanotaxis. I. Die anodische Gal- 

 vanotaxis. Zeitschr. f. Allg. Physiol., Bd. ii, pp. 341-384. 

 '03 — Zur Kenntniss der Galvanotaxis. II. Eine Analyse der Galvano- 

 taxis bei Spirostomum. Zeitschr. f. Allg. Physiol., Bd. ii, pp. 516— 

 555- 



