550 RHYTHMS IN PLANTS AND ANIMALS 



3. Phase-shift induction by UV is photoreversible by radiant 

 energy from the visible region of the spectrum. 



A cknowledgment 



I am grateful to Mrs. Janet Fraembs for her very capable assistance. 



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Ehret, C. F. 1953. An analysis of the role of electromagnetic radiations in the 



mating reaction of Paramecium bursaria. Physiol. ZooL, 26, 274-300. 

 Ehret, C. F. 1955a. The effects of pre- and post-illumination on the scotophilic 



recovery phase of the Paramecium bursaria mating reaction. Anat. Record, 



122, 465-57. 

 . 1955b. The photoreactivability of sexual activity and rhythmicity in 



Paramecium bursaria. Rad. Research, 3, 222-23. 

 Kimball, R. F., and N. Gaither. 1951. The influence of light upon the action of 



ultraviolet in Paramecium aurelia. J. Cellular Comp. Physiol., 37, 211-33. 



