484 HADIATION HIOLOGY 



photoreactivatiiij? liglit in hacteriopluige T2 in sinjjjle infection (Sect. 3-5), 

 by a small number of li^lit (luaiita in the same phafi;o in multiple infection 

 (Sect. 3-7), and in pha^e 'r3 in single infection (Sect. 3-0); by a larger 

 luimber of (juanta in bacteria (Sect. 4-4). It is possible that at an ele- 

 mentary le\el of organization photoreactivation is a one-cjuantum phe- 

 nomenon, and that higher numbers of quanta are recjuired at higher levels. 

 More extensive kinetic investigations would be desirable in various types 

 of microorganisms. 



7. The photoreactivation of the mutagenic effect generally appears as a 

 constant ultraviolet dose reduction (Sect. 5-7 and Sect. 6), indicating the 

 intimate similarity with the photoreactivation of the killing effect. The 

 two effects could be chemically identical but biologically different owing 

 to a different localization of the changes responsible for them. 



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