SIAGES IN PHAGE MULTIPLICATION 187 



The phage-specific protein precursors include materials that 

 sediment like doughnuts as well as smaller fragments, in approxi- 

 mately equal amounts as measured by sulfur content (Hershey, 

 1956b). 



7. Conclusion 



Phage growth is initiated by the injection of the viral DNA into 

 the cell. Completed phage particles do not reappear until the 

 mid-point of the latent period. Morphologically recognizable 

 elements are formed somewhat earlier. Radiobiological analy- 

 sis of phage growth also shows that important processes occur 

 during the eclipse period of viral growth. These and other 

 lines of evidence suggest that noninfective phage particles, called 

 vegetative phage, are multiplying during the period of eclipse. 



Attempts to enumerate vegetative phage particles in infected 

 cells by radiobiological methods have generally failed. Instead 

 the experiments show that vegetative phage T2 is remarkably 

 resistant to ultraviolet light, X-rays, and decay of constituent 

 radiophosphorus. Vegetative phage T7 does not show this 

 property. For this and other reasons the proper interpretation 

 of the radiobiological experiments is not clear. 



