This journal provides immediate access to some articles. Volume 6(2); February 1920 Anthropology Central American Calendars and the Gregorian Day PMCID: PMC1084405 Astronomy The Larger Opportunities for Research on the Relations of Solar and Terrestrial Radiation PMCID: PMC1084415 Chemistry An Apparent High Pressure Due to Adsorption, the Heat of Adsorption, and the Density of Gas-Mask Charcoals PMCID: PMC1084404 Genetics Selective Fertilization in Pollen Mixtures PMCID: PMC1084410 Model of the Linkage System of Eleven Second Chromosomegenes of Drosophila PMCID: PMC1084412 Mathematics Groups Generated by Two Operators, s1, s2, Which Satisfy the Conditions s1m = s2n, (s1s2)k = I, s1s2 = s2s1 PMCID: PMC1084411 Pathology Calcium and Magnesium Metabolism in Certain Diseases PMCID: PMC1084414 Physics The Torsional Magnetic Energy Absorption of an Iron Conductor PMCID: PMC1084406 A Study of Absorption Spectra with the Electric Furnace PMCID: PMC1084408 A Study of the Effect of a Magnetic Field on Electric Furnace Spectra PMCID: PMC1084409 Physiology The Adjustment to the Barometer of the Hematorespiratory Functions in Man PMCID: PMC1084407 Zoölogy The Development of Connective Tissue in the Amphibian Embryo PMCID: PMC1084413 On the Hyperplasia of Nerve Centers Resulting from Excessive Peripheral Loading PMCID: PMC1084416 Journal Matter Original table of contents page Administrative content — journal masthead, notices, indexes, etc. | ||