This journal provides immediate access to some articles. Volume 32(5); May 1946 Bacteriology Strain Specificity and Production of Antibiotic Substances: VII. Production of Actinomycin by Different Actinomycetes PMCID: PMC1078897 Growth Requirements of Virus-Resistant Mutants of Escherichia Coli Strain “B” PMCID: PMC1078898 Genetics Experiments on Sexual Isolation in Drosophila: VII. The Nature of the Isolating Mechanisms Between Drosophila Pseudoobscura and Drosophila Persimilis PMCID: PMC1078899 Two Types of Heterochromatin in Drosophila Nebulosa PMCID: PMC1078900 Genes Which Divide Species or Produce Hybrid Vigor PMCID: PMC1078901 Mathematics Prime Number of Operators in Sets of Conjugates PMCID: PMC1078902 Comparison of Union-Preserving and Contact Transformations PMCID: PMC1078903 An Ergodic Theorem PMCID: PMC1078904 Journal Matter Original table of contents page Administrative content — journal masthead, notices, indexes, etc. | ||