CONTENTS 
Page 
G^NBTics. — H0MO1.OGOUS Genes and Linear Linkage in Drosqphila virilis. 
By Alexander Weinstein 625 
Physics. — The Intensities of X-Rays of the L-Series, III. Critical 
P0TENT1A1.S OF THE P1.AT1NUM AND Tungsten Lines 
By Frank C. Hoyt 639 
Mathematics. — Semivariants of a General System of Linear Homogeneous 
Differential Equations By E. B. Stouffer 645 
Physics. — Some New Methods in Interior Ballistics 
By Arthur Go f don Webster 648 
Genetics. — The Mutant Crossveinless in Drosophila melanogaster . . 
By Calvin B. Bridges 660 
Is Crossing Over a Function of Distance? 
By J. A. Detlefsen 663 
Interspecific Hybrids in Crepis "... 
By E. B. Babcock and J. L. Collins 670 
Astronomy. — New Observations on the Variability of the Sun .... 
By C.G. Abbot 674 
Mathematics. — The Permanent Gravitational Field in the Einstein 
Theory By L. P. Eisenharl 678 
Statistics. — Simplified Method for the Statistical Interpretation of 
Experimental Data By George A. Linhart 682 
Agriculture. — ^A Critical Study of Fertilizer Experiments ..... 
By C. B. Lipman and G. A. Linhart 684 
