OP ARTS AND SCIENCES. 87 



EXPLANATION OF FIGURES. 



These diagrams are designed to show the serial relationship of the eyes and 

 segmental papilhv;, the abbreviation of tlie end somites, the relative positions of 

 the sexual orifices, nepliri<lial pores, papilla^, &c. 



Fig. 1 illustrates these points in the Medicinal Leech. 



Fig. 2 represents the first seven somites of the Land Leech (Hajmadipsa). 



Fig. 3 shows the five posterior somites of the same. 



Fig. 4 represents the posterior abbreviated somites of Macrobdella. 



Fig. 5 represents the same somites in Microstoma. 



The numerals on the left indicate the number of somites ; those on the right 

 mark the first ring of each somite. Tlie eyes are indicated by large black dots ; 

 tlie segmental papiliie, by smaller dots ; and the nephridial pores, by short 

 dashes (lst-17tliyj). 



1-5 oi. The five pairs of eyes. 



7n. Median papillae. 



il. Inner lateral papilla?. 



ol. Outer lateral pnpiilte. 



7ng. Marginal papillae. 



a. Anus. 



80-31. Position of male orifice. 



85-36. Position of female orifice. 



