CONTRIBUTIONS TO THE ANATOMY OF THE HIEUDINEA. 457 



Fig. 2. — Diagram of a transverse section of Pontobdella. 

 Fig. 3. — Similar diagram of Clepsine. 

 Fig. 4. — Similar diagram of Hirudo. 



Fig. 5. — Similar diagram of Nephelis. 



Al. Alimentary canal, te. Testis, ov. Ovary, n. c. Nerve-cords. 

 n.f. Nephridial funnel, n. a. External aperture of nephridium. d. s. 

 Dorsal sinus, v. s. Ventral sinus. /. s. Lateral sinus, d. v. Dorsal 

 vessel. V. v. Ventral vessel. I. v. Lateral vessel. 



These diagrams indicate the amount of vascular space which occurs in 

 these various genera, whether vascular or ccelomic. The vascular spaces 

 are marked by a thickened striated contour, while the ccelomic spaces are 

 drawn with the single line limiting them. 



