CONTENTS 



III. Chemistry of Virus Strains 139 



A. Protein Components 139 



B. Nucleic Acids 146 



IV. Production of Variants by Chemical and Physical Treatments 150 



A. Chemical Derivatives of TMV 151 



B. Relation of Radiations to Production of Variants 152 



V. Summary and Perspectives 152 



References 153 



rV. Biological Cycles of Plant Viruses in Insect Vectors by L. M. Black 157 



I. Introduction 157 



II. The Nature of the Insects and Viruses Involved in Biological 



Cycles 159 



III. History of Research on the Problem 161 



IV. Evaluation of Kinds of Evidence for Multiplication 173 



V. Evaluation of Kinds of Evidence for Absence of Multiplication 175 



VI. Significance of Biological Cycles 179 



References 184 



V. Bacteriophage as a Model of Host- Virus Relationship by Andre 



LwoFF 187 



I. Introduction 187 



II. The Bacteriophage 189 



A. The Vegetative Phase 189 



B. The Proviral Phase and the Lysogenic Bacterium 190 



III. The Origin of Bacteriophage 191 



IV. Is Bacteriophage an Organism? 192 



V. Bacteriophage and Cellular Organelles 193 



VI. Bacteriophage as a Virus 195 



VII. Are Viral Diseases Always Infectious? 197 



VIII. Remarks on the Pathogenicity of Viruses 198 



IX. Conclusions 200 



References 201 



VI. The Initiation of Bacteriophage Infection by Alan Garen and 



Lloyd M. Kozloff 203 



I. Introduction 204 



II. Morphology and Composition of Bacteriophages 204 



A. Size and Shape 204 



B. Chemical and Morphological Components 205 



C. Properties of the Components of Phage T2 208 



III. The Bacterial Surface 210 



IV. Injection 211 



