CONTENTS 



Introduction by Joshua Lederberg ix 



Mutations of Bacteria from Virus Sensitivity to Virus Resistance, by 

 S. E. Luria and M. Delbruck 3 



The Distribution of the Numbers of Mutants in Bacterial 



Populations, by D. E. Lea and C. A. Coulson 24 



Origin of Bacterial Variants, by Howard B. Newcombe 46 



Delayed Phenotypic Expression of Spontaneous Mutations in Escherichia 



coli, by Howard B. Newcombe 49 



Origin of Bacterial Resistance to Antibiotics, by M. Demerec 79 



Chloromycetin Resistance in E. coli, a Case of Quantitative Inheritance 



in Bacteria, by L. L. Cavalli and G. A. Maccacaro 91 



Studies on Nutritionally Deficient Bacterial Mutants Isolated by Means 



of Penicillin, by Bernard D. Davis 94 



The Demonstration of Non-specific Components in Salmonella paratyphi 



A by Induced Variation, by D. W. Bruner and P. R. Edwards 104 



The Natural Occurrence of Phase 2 of Salmonella paratyphi A, 



by P. R. Edwards, L. A. Barnes, and Mary C. Babcock i 16 



Changes Induced in the O Antigens of Salmonella, by D. W. Bruner 



and P. R. Edwards 118 



Mutations in Escherichia coli Induced by Chemical Agents, 



by Evelyn M. Witkin 119 



The Effect of Metabolites upon Growth and Variation of Brucella 

 abortus, by Robert J. Goodlow, Leonard A. Mika, and Werner 

 Braun 133 



Gene Recombination and Linked Segregations in Escherichia coli, 



by Joshua Lederberg 143 



Aberrant Heterozygotes in Escherichia coli, by Joshua Lederberg 164 





