276 FRANK E, BEDDARD. 



ovorum. ov. Mature ovum with membrane, germ, Germinal cells attached 

 to ovum. 



Fig. 30. — Hyperiodrilus. Transverse section through unpaired oesopha- 

 geal pouch, to show blood-spaces {black) and lamina between folds of 

 epithelium. 



Fig. 31. — Hyperiodrilus, Origin of unpaired oesophageal pouch (e«.). 

 d. Glandular (?) cells found among the ordinary epithelial cells, p. Peri- 

 toneum. 



PLATE XIX. 



Heliodrilus lagosensis. 



Figs, 32 — 34, — A series of sections to show the investment of the apex of 

 the spermatheca by coelomic spaces. 



Fig. 32. The apex of the spermatheca {sperm.) lies between two out- 

 growths of the coelomic sac {coel.). 

 Fig. 33. The apex of spermatheca [sp.) is now enclosed within the 

 coelomic sac, and the commencement of a second coelomic space 

 within the first is just visible. 

 Fig. 34. This section lies beyond the apex of spermatheca, which just 

 reaches the interior of the sac [coel'.), lying within that {ecelom) which 

 is continuous with the perigonadial sac. 

 Fig. 35. — Diagrammatic representation of the extremity of the sperma- 

 theca {sp.) enclosed within a sac, which is itself enclosed within an extension 

 of the perigonadial sac ; the narrow canal leading from the latter to the ovary 

 is seen. Portions of the walls of the different sacs are removed to show 

 their contents. 



Fig. 36. — Section through dilated portion of vas deferens with surrounding 

 coelomic sac. vd. e. Ciliated epithelium of vas deferens, p. Peritoneum 

 covering coelomic sacs ; in its interior are seen clumps of cells. 



Fig. 37. — Section showing structure of spermatheca. ep. Epithelium. 

 gr. Granular matter tiirowu off from cells into the interior of the spermatheca. 

 m. Muscular coat with blood-vessels, shown black. 



Fig. 38. — Section showing structure of distal part of atrium, vmsc. Mus- 

 cular coat. n. Nuclei of innermost epithelial layer. 



Fig. 39. — Section showing structure of atrium, near to its external orifice. 

 Large glandular cells {gl?) are seen, separated by interstitial cells, muse. 

 Muscular coat. 



Fig. 40. — Section through common orifice of atrium and nephridium. 

 Fig. 41. — Diagram of female reproductive system, sperm. Spermatheca. 

 sp. 0. Its external orifice, ov. Ovarian sac, represented as being cut open on 



