Proceedings of the American Academy of Arts and Sciences. 

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



CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE | 



MUSEUM OF COMPARATIVE ZOr)LOGY AT HARVARD COLLEGE. ' 



E. L. MARK, DIRECTOR. — No. 108. 



THE METAMERISM OF THE HIRUDINEA. 



By W. E. Castle. 



