VOL. XLVI, HO. 643 



MARCH, 1812 



THE 



AMERICAN 

 NATURALIST 



A MONTHLY JOURNAL 

 Devoted to the Advancement of the Biological Sciences 1 

 Special Eeference to the Factors of Evolntion 



I. Problem* of Evolution andtPresent Methods of Attacking them. 



Professor Edwin G. Conkain 

 H. Light thrown by the Experimental study of Heredity upon the Factors and 

 Methods of Evolution. Dr. C. B. Davenport 



III. Biotypes and"Phylogeny. Dr. Httbebt Lyman Clabk 



IV. Shorter Articles and Discussion : A Literary Note on Mendel's Law. Dr. W. 



W. Stockbebgeb. The Range of Size in the Vertebrates. Dr. Arthttb W. 



•edity. Dr. W. J. Spillman. The Distribution of 

 Plants in North America. Professor Douglas Houghton Campbell - 



THE SCIENCE PRESS 

 LANCASTER, PA. GARRISON, JT. T. 



HEW YORK : SUB-STATION 84 



