HELIOTROPISM, DIFFERENTIAL SENSIBILITY/ AND 



GALVANOTRISM IN EUGLENA 

 A 



FRANK W. BANCROFT 



Department of Experimental Biology, Rockefeller Institute for Medical 

 Research, New York 



FIVE FIGURES 



CONTENTS 



• 



1. Introduction 384 



2. Historical review 385 



A. The "local action tropism theory" 386 



B. Position of Jennings and Mast on direct orientation 389 



3. Methods and material 394 



4. Normal locomotion 395 



5. The facts of heliotropic orientation 398 



A. Correlation between the sign of the heliotropism and the sign of the 

 differential reaction 398 



B. Correlation of gradual heliotropic orientation and differential reactions 

 with respect to the presence and absence of these two factors 402 



C. Sensitization, fatigue and recovery 404 



D. Orientation with and without shock-movements 406 



E. Time required for stimulation 407 



F. No blending of shock-movements and tropism as the light is dimin- 

 ished 409 



G. How is Euglena kept oriented? : 410 



H. Galvanotropism and heliotropism 412 



I. Conclusions 414 



6. The Nature of the stimulus 417 



A. Criteria for distinguishing reactions due to differential and constant 

 light action 418 



B. Experimental data 421 



a. Continuous widening of the spiral 421 



b. Orientation maintained by continuous light action 423 



c. Heliotropism and variations in the rapidity of the change in 



illumination 423 



C. Conclusions 424 



7. Summary 425 



8. Bibliography 428 



^Differential sensibility is used as synonymous with Unterschiedsempfind- 

 lichkeit. 



383 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 15, NO. 4 

 NOVEMBER, 1913 



