THE JOURNAL 



OF 



EXPERIMENTAL ZOOLOGY 



EDITED BY 



WILLIAM E. CASTLE 



Harojard Unvuersity 

 EDWIN G. CONKLIN 



Princeton Uni'versity 

 CHARLES B. DAVENPORT 



Carnegie Institution 

 HORACE JAYNE 



The Wistar Institute 

 HERBERT S. JENNINGS 



Johns Hopkins Uni'versity 



FRANK R. LILLIE 



Uni'-versity of Chicago 

 JACQUES LOEB 



Vni-uersity of California 

 THOMAS H. MORGAN 



Columbia Uni-uersity 

 GEORGE H. PARKER 



Harvard Uni-Tjersity 

 CHARLES O. WHITMAN 



Uni'versity of Chicago 



EDMUND B. WILSON, Columbia Uni'versity 



and 



ROSS G. AaRRISON, Tale Uni'versity 

 Managing Editor 



VOLUME VI 



PUBLISHED EIGHT TIMES A YEAR BY 



THE WISTAR INSTITUTE OF ANATOMY AND BIOLOGY 



36th STREET AND WOODLAND AVENUE 



PHILADELPHIA, PA. 



