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Volume 26(4);  April 15, 1940
Anthropology and Psychology
The Effect of an “Emotional State” on the Initial Stages of Acquisition in a Conditioned Operant Response
R. M. Gagné and C. H. Graham
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 297–300.
PMCID: PMC1078177
Astronomy
The Absolute Magnitudes of Stars of High Luminosity
Jesse L. Greenstein
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 259–264.
PMCID: PMC1078168
Synthetic Spectra for Supernovae
Cecilia Payne-Gaposchkin and Fred L. Whipple
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 264–272.
PMCID: PMC1078169
Botany
Cytoplasmic Behavior during Division of Vacuolate Plant Cells
Edmund W. Sinnott and Robert Bloch
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 223–227.
PMCID: PMC1078159
Chemistry
Micelle Formation in Aqueous Solutions of Digitonin
Emil L. Smith and Edward G. Pickels
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 272–277.
PMCID: PMC1078170
Genetics
Further Observations on the Mechanism of Induced Chromosome Rearrangement in Sciara
C. W. Metz and Martha Lee Bozeman
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 228–231.
PMCID: PMC1078160
Conjugation of Three Animals in Paramecium Bursaria
Tze-Tuan Chen
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 231–238.
PMCID: PMC1078161
Polyploidy in Paramecium Bursaria
Tze-Tuan Chen
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 239–240.
PMCID: PMC1078162
Evidences of Exchange of Pronuclei during Conjugation in Paramecium Bursaria
Tze-Tuan Chen
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 241–243.
PMCID: PMC1078163
Conjugation in Paramecium Bursaria between Animals with Very Different Chromosome Numbers and between Animals with and without Micronuclei
Tze-Tuan Chen
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 243–246.
PMCID: PMC1078164
Mathematics
A Set of Postulates for Bolyai-Lobatchevsky Geometry
Frederick P. Jenks
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 277–279.
PMCID: PMC1078171
A General Theory of Spectra. I: I
M. H. Stone
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 280–283.
PMCID: PMC1078172
The Groups Which Contain Exactly Fourteen Proper Subgroups
G. A. Miller
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 283–286.
PMCID: PMC1078173
Equilong Symmetry with Respect to Any Curve
Edward Kasner
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 287–291.
PMCID: PMC1078174
Partially Ordered Sets and Topology
Arthur N. Milgram
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 291–293.
PMCID: PMC1078175
On the Distribution of Normal Point Groups
P. Erdős
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 294–297.
PMCID: PMC1078176
Physics
Note on the Problem of the Distribution of Stress in a Thin Stiffened Elastic Sheet
Eric Reissner
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 300–305.
PMCID: PMC1078178
On Some Periodic Properties of the System of Isotopes
Arthur E. Haas
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 305–312.
PMCID: PMC1078179
Mechanism of Long Wave-Length Absorption of the Carbonyl Group
Henry L. McMurry and Robert S. Mulliken
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 312–317.
PMCID: PMC1078180
Zoölogy and Anatomy
Novel Types of Nerve Reflexes
G. H. Parker
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 246–249.
PMCID: PMC1078165
Agglutination of Sea-Urchin Eggs by Means of a Substance Extracted from the Eggs
Albert Tyler
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 249–256.
PMCID: PMC1078166
Diurnal Variation of Intermedin in the Blood of the Albino Rat
Leon Levinson
Proc Natl Acad Sci U S A. 1940 April 15; 26(4): 257–258.
PMCID: PMC1078167
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