TOL. XLVI, 80. 545 



THE 



AMERICAN 

 NATURALIST 



A MONTHLY JOURNAL 

 Devoted to tlie Advancement of the Biological Science! i 

 Special Beferenee to the Factors of Evolntion 



CONTENTS 



L The Continuous Origin of Certain Unit Characters as Observed bj 



tologist. Dr. Henby Fairfield Osborn - 

 H. The Biology of the Crayfish. Dr. F. E. Chidesteb - - 

 in. Present Problems in Soil Physics as related to Plant Activities, 



Burton E. Livingston - 



IV. Shorter Articles and Discnssion : Farther Notes regarding Sele< 

 Numbers: Professor Raymond Peabi, - - 

 Notes and Literature: Protozoa: Professor Chables Atwoo 

 Heredity : Dr. W. J. SPIIXMAN 



THE SCIENCE PRESS 

 LANCASTER, PA. GABBXSON, N. Y. 



HEW YOKE : STXB-BTATIGK S4 



