1830. ANNIYERSAEY MEIOIRS OF THE BOSTON SOCIETY OF NATURAL HISTORY. 1880. 



THE DEVELOPMENT 



OF A 



DOUBLE-HEADED VERTEBRATE. 



By SAMUEL F. CLARKE, Ph.D., 



ASSISTANT IN BIOLOGY, JOHNS HOPKINS UNIVERSITY, BALTIMORE, MD. 



BOSTON: 



PUBLISHED BY THE SOCIETY. 

 1880. 



