PRECURSORS OF PHAGE 



57 



TABLE I 



RELATION OF THE YIELD OF PHAGE PER BACTERIAL CELL 



TO THE AMOUNT OF BACTERIAL N CONTRIBUTED 



TO PHAGE PROTEIN AND NUCLEIC ACID 



'Arranged in order of increasing yield. 



lished by experiments in which phage samples were taken and analyzed 

 at different times after infection (Table II). 



In any given experiment the N^^ content of the phage nucleic acid 

 is nearly independent of the time of sampling, but the N" content of 

 the phage protein falls with time. The differential utilization of host 

 N is most marked in the later time intervals. The data are in accord 

 with the hypothesis that the phage nucleic acid N is partially derived 

 from a stable precursor (possibly DNA) and the phage protein N is 



