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Volume 20(4);  April 1934
The cover of the journal
Chemistry
Fused “Onium” Salts as Acids: I. Reactions in Fused Ammonium Nitrate
L. F. Audrieth and M. T. Schmidt
Proc Natl Acad Sci U S A. 1934 April; 20(4): 221–225.
PMCID: PMC1076384
Genetics
Norms of Pollen-Tube Growth in Incompatible Matings of Self-Sterile Plants
E. M. East
Proc Natl Acad Sci U S A. 1934 April; 20(4): 225–230.
PMCID: PMC1076385
A New Gene Affecting Behavior and Skeleton in the House Mouse
L. C. Dunn
Proc Natl Acad Sci U S A. 1934 April; 20(4): 230–232.
PMCID: PMC1076386
Mathematics
Groups Involving Three and Only Three Squares
G. A. Miller
Proc Natl Acad Sci U S A. 1934 April; 20(4): 243–246.
PMCID: PMC1076390
Physics
Projective Differentiation of Spinors
J. W. Givens, Jr.
Proc Natl Acad Sci U S A. 1934 April; 20(4): 232–233.
PMCID: PMC1076387
Physiology and Biochemistry
The Extinction of Chained Reflexes
B. F. Skinner
Proc Natl Acad Sci U S A. 1934 April; 20(4): 234–237.
PMCID: PMC1076388
Anomalies in the Absorption Spectrum of Visual Purple
Selig Hecht and Aurin M. Chase
Proc Natl Acad Sci U S A. 1934 April; 20(4): 238–243.
PMCID: PMC1076389
Zoölogy and Anatomy
Heterotopic Spinal Cord Grafts in Salamander Embryos
W. M. Rogers
Proc Natl Acad Sci U S A. 1934 April; 20(4): 247–249.
PMCID: PMC1076391
Journal Matter
Administrative content — journal masthead, notices, indexes, etc.
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