This journal provides immediate access to some articles. Volume 20(2); February 1934 Astronomy The Diameter of the Andromeda Nebula PMCID: PMC1076348 Botany Haploids in Hordeum Vulgare PMCID: PMC1076349 Genetics Possible Cytoplasmic as Well as Chromosomal Control of Sex in Haploid Males PMCID: PMC1076350 Mutation Rate Increased by Aging Seeds as Shown by Pollen Abortion PMCID: PMC1076351 Three Cases of Deficiency in Chromosome 9 of Zea mays PMCID: PMC1076352 Mathematics Minimum Number of Squares in a Group When Not All of Them Are Relatively Commutative PMCID: PMC1076357 General Theorems on Trajectories and Lines of Force PMCID: PMC1076358 On the Metrical Transitivity of the Geodesics on a Surface of Constant Negative Curvature PMCID: PMC1076359 On the Theory of Laplace Integrals: II PMCID: PMC1076360 Physics Notes on Intensities in the Spectrum O II PMCID: PMC1076353 On the Vector Model for Almost Closed Shells PMCID: PMC1076354 Physiology and Biochemistry Can Mammalian Eggs Undergo Normal Development in Vitro? PMCID: PMC1076355 Achromobacter Ichthyodermis, N. Sp., The Etiological Agent of an Infectious Dermatitis of Certain Marine Fishes PMCID: PMC1076356 Journal Matter Administrative content — journal masthead, notices, indexes, etc. | ||