VOI. XIIX, NO. 583 



JULY, 1915 



THE 



AMERICAN 

 NATURALIST 



A MONTHLY JOURNAL 

 Devoted to the Advancement of the Biological Science* with 

 Special Reference to the Factors of Evolution 



CONTENTS 



THE SCIENCE PRESS 

 i-ANOASTER, PA. GARRISON, N. t 



NEW YORK : SUB-STATION 84 



