lStronomy. — A Possible Origin for Some Spiral Nebulae. By George F. 
Soil Chemistry— A Peculiar Clay from near the City of Mexico . 
By E. W. Hilgard 
Astronomy. — Studies of Magnitudes in Star Clusters, I. On the Absorption 
OF Light in Space By Harlow Shapley 12 
Astronomy.— Studies of Magnitudes in Star Clusters, II. On the Sequence 
OF Spectral Types in Stellar Evolution By Harlow Shapley 15 
Physics. — ^Experimental Evidence for the Essential Identity of the Selective 
AND Normal Photo-Electric Effects . By R. A. Millikan and W. H. Sotider 19 
Geophysics. — Concomitant Changes in Terrestrial Magnetism and Solar Radia- 
tion By L. A. Bauer 24 
Geology. — Sub-Marine Solution of Limestone in Relation to the Murray- 
Agassiz Theory of Coral Atolls By Alfred Goldshorough Mayer 28 
Botany. — ^The Archegonium and Sporophyte of Treubia Insignis Goebel . . . 
By Douglas Houghton Campbell 30 
Anthropology. — Brief Notes on Recent Anthropological Explorations Under 
THE Auspices of the Smithsonian Institution and the U. S. National Mu- 
seum By Ales Hrdlicka 32 
Physiology. — ^A Theory of Nerve-Conduction . By Alfred Goldsborough Mayer 37 
Anthropology. — Zuni Culture Sequences By A. L. Kroeber 42 
Genetics. — ^The Numerical Results of Diverse Systems of Breeding .... 
^ By H. S. Jennings 45 
Zoology. — On the Effects of Feeding Pituitary Body (Anterior Lobe) Sub- 
stance, AND Corpus Luteum Substance to Growing Chicks ...... 
By Raymond Pearl 50 
Genetics.— A Preliminary Report on Further Experiments in Inheritance and 
Determination of Sex By Richard Goldschmidt 53 
Genetics. — On the Degree of Inbreeding which Exists in American Jersey 
Cattle ........... By Raymond Pearl and S. W. Patterson 58 
Mathematics. — ^Upper Limit of the Degree of Transitivity of a Substitution 
Group By G, A. Miller 61 
Geology. — ^The Extension of the Montana Phosphate Deposits Northward 
into Canada By Frank D. Adams and W. J. Dick 62 
