This journal provides immediate access to some articles. Volume 25(9); September 1939 Astronomy The Gravitational Motion of a Pair of Rigid Bodies PMCID: PMC1077948 Botany Developmental Changes in Apical Meristems PMCID: PMC1077943 Chemistry The Synthesis of Sulfonyl Chlorides by Chlorination of Sulphur Compounds PMCID: PMC1077944 Development of Eye-Colors in Drosophila: Bacterial Synthesis of v + Hormone PMCID: PMC1077952 Nutritional Requirements of Drosophila Melanogaster PMCID: PMC1077953 Genetics Hybridization and Tumor Formation in Mice PMCID: PMC1077945 Nuclease Action, Protease Action and Histochemical Tests on Salivary Chromosomes of Drosophila PMCID: PMC1077946 Mathematics A Theory of Length and Its Applications to the Calculus of Variations PMCID: PMC1077949 General Trihornometry of Second Order PMCID: PMC1077950 Groups Which Contain Less Than Ten Proper Subgroups PMCID: PMC1077951 Psychology and Anthropology Adjusted Death Rates PMCID: PMC1077947 Journal Matter Administrative content — journal masthead, notices, indexes, etc. | ||