

BIOLOGY 



LIBRARY 



G 



COMMISSION 



TO WHICH THIS MEMOIR HAS BEEN REFERRED. 



PROF. C. D. MEIGS. 

 THADDEUS W. HARRIS, M. D. 



Ub, 



JOSEPH HENRY, Secretary. 







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CAMBRIDGE : 

 METCALF AND COMPANY, 



PRINTERS TO THE UNIVERSITY. 



