/ 



VOL. XLIX, NO. 579 



MARCH, 1915 



THE 



AMERICAN 

 NATURALIST 



A MONTHLY JOURNAL 

 Devoted to the Advancement of the Biological Sciences with 



Special Reference to the Factors of Evolution 



CONTENTS 



Page 



I. Mutation en Masse. Harley Habeis Baktlett W» 



n. The Albino Series of Allelomorphs in Guinea-pigs. Sewall Wright - 140 

 ni. Progressive Evolution and the Origin of Species. Professor Arthur Dendy 149 

 IV. Shorter Articles and Discussion: The Origin of a New Eye-Color in Droso- 

 phila repleta and its Behavior in Heredity: Roscoe R. Hyde; A Wing 

 Mutation in a New Species of Drosophila . Roscoe R. Hyde: Mutations 

 in Two Species of Drosophila: C. W. Hi I ai B.S.Mei A Sex-linked 



THE SCIENCE PRESS 

 LANCASTER, PA. GARRISON, N. T. 



NEW YORK : SUB-STATION 84 



