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CONTENTS 
PHYSIOI.OGY. — ^Thb Dynamics of a Fi^uctuating Growth Ratb 
By H. S. Reed 397 
Biology. — ^Anai^yticai, Note on Certain Rhythmic Rei^ations in Organic 
Systems : By Alfred J. Lotka 410 
Mathematics. — On the Ci^ass Number of the Fiei^d * '^//)**) and the 
Second Case of Fermat's Last Theorem By H. S. Vandiver 416 
Genetics. — Observations on the Sterility of Mutant Hybrids in Droso- 
phila Virilis By C. W. Metz 42 1 
Zoology. — Studies on the Transformation op the Intestinal Flora, ^th 
Special Reference to the Implantation of Bacillus Acidophilus 
I. Feeding Experiments with Albino Rats 
By Harry A. Cheplin and Leo F. Rettger 423 
Statistics. — On a Single Numerical Index of the Age Distribution of a 
Population By Raymond Pearl 427 
Zoology. — ^Upon an Important Method of Studying Problems of Relation- 
ship and of Geographical Distribution .... jBy Maynard M. Metcalf 432 
Botany. — The Influence of Cold in Stimulating the Growth of Plants . . 
By Frederick V. Coville 434 
Physics. — On the Nature of the Negative Carriers Produced in Pure* 
Hydrogen and Nitrogen by Photo-Electrons. .By Leonard B. Loeb 435 
Engineering. — Shock or Water Ram in Pn>E Lines with Imperfect Re- 
flection AT THE Discharge End and Including the Effects of Friction 
and Non-Uniform Change of Valve Opening By W. F. Durand 441 
Report of the Annual Meeting 442 
