Proceedings of the American Academy of Arts and Sciences. 

 Vol. XXXV. No. 15. — February, 1900. 



CONTRIBUTIONS FROM TI1K ZOOLOGICAL LABORATORY OF THE 

 MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. 

 K. L. MARK, DIRECTOR — No. 108. 



THE METAMERISM OF THE HIRUDINEA. 



By W. E. Castle. 



