CONTENTS 
Page 
Genetics.' — The Effect of Artificial Selection on Bristle Number in Droso- 
phila ampelophtla and its Interpretation . ... By Femandus Payne 55 
Zoology.' — The Reactions of the Melanophores of Amiurus to Light and to 
Adrenalin By A. W. L. Bray 58 
Zoology.— Further Experiments on the Sex of Parthenogenetic Frogs . . 
By Jacques Loeb 60 
Physics. — The Resolving Powers of X-Ray Spectrometers and the Tungsten 
X-Ray Spectrum By Elmer Dershem 62 
Physics. — Note on Methods of Observing Potential Differences Induced by 
the Earth's Magnetic Fleld in an Insulated Moving Wire 
By Carl Barus and Maxwell Barus 66 
Astronomy. — Dependence of the Spectral Relation of Double Stars Upon 
Distance By CD. Perrine 71 
Astronomy . — Hypothesis to Account for the Spectral Conditions of the 
Stars By CD. Perrine 75 
National Research Council. — Meetings of the Executive Committee 
76 
