This journal provides immediate access to some articles. Volume 7(5); May 1921 Astronomy Measurement of the Diameter of Alpha-Orionis by the Interferometer PMCID: PMC1084808 Studies of Magnitudes in Star Clusters: XIII. Variable Stars in N. G. C. 7006 PMCID: PMC1084811 Genetics The Influence of Age on Fertility in Swine PMCID: PMC1084806 Variation and Inheritance in Size in Trypanosoma lewisi: 1. Life-cycle in the Rat and a Study of Size and Variation in “Pure Line” Infections PMCID: PMC1084807 The Globe, a Simple Trisomic Mutant in Datura PMCID: PMC1084810 Mathematics An Overlooked Infinite System of Groups of Order pq2 PMCID: PMC1084809 Physics The Diffusion of Air through Water in the Lapse of Years PMCID: PMC1084805 Zoölogy The Skin Temperature of Pachyderms PMCID: PMC1084812 Journal Matter Original table of contents page Administrative content — journal masthead, notices, indexes, etc. | ||