454 



HOWARD B. NEWCOMBE 

 Table 1 



Estimates of mutation rate o/B/r to resistance to phage Tl, using the methods of LURIA and DEL- 

 BRtJCK (1943) (methods 1 and 2 in the present paper) , calculating from the number of cultures 

 with no resistant bacteria, and from the average number of resistant bacteria per culture, respectively, 

 in series of similar cultures started from small inocula. 



Assays were made of total bacteria and of numbers of resistant individuals 

 in the inocula and in the fully grown test cultures. These four values are desig- 

 nated Ni, ti, N2 and r 2 , respectively. For the sake of accuracy, five or ten inde- 

 pendent assays were made in each case. The number of generations of growth, 

 g, was determined for each of the cultures from the values N x and N2. 



56 



