382 W. BLAXLAND BENHAM. 



Fig. 8.— a longitudinal section of the atrium and neigbbouring parts. 

 The Septum x/xi is seen passing forwards underneath the atrium to be in- 

 serted near anterior boundary of the somite (of. Fig. 5) where this septum 

 coalesces with Septum xi/xii. circ. m. Circular muscles of the body-wall. 

 cce. ep. Ccelomic epithelium outside the prostate, gl. The glandular region of 

 the duct of the atrium, long, m. Longitudinal muscles of the body-wall, a 

 portion of which is continuous with the muscular wall of the atrial duct. 

 muUicell. gl. Pyriform groups of gland-cells projecting outside the muscular 

 coat {mus. coat) of the atrium, and whose necks traverse this coat, neph. 

 Portion of nephridium in Somite xi. ohl. in. Oblique muscles, some amongst 

 the longitudinal and others amongst the muscles of the atrial wall. ov. Por- 

 tion of ovary, ovd. Edge of the funnel of the oviduct, p. Prominence of the 

 lining of the atrium, on the apex of which (in another section) ihe sperm- 

 duct opens, sp. d. Portion of sperm-duct in the wall of the atrium. 



Fig. 9. — A portion of the prostate (wall of the atrium) greatly magnified. 

 One group of gland-cells is represented in detail ; the necks of the cells are 

 readily traced through the muscular coat {mus.), but not so readily traced up 

 to the epithelium {ep.). The latter is, however, traversed by narrow ducts 

 (as at a), which are, no doubt, the necks of the gland-cells. Between the 

 epithelium and the muscular coat are large pyriform glands, the details of 

 which could not be made out owing to the preservation of the material, b. v. 

 Blood-vessels. 7i. per. Nucleus of flat ccelomic epithelial cells, which surround 

 the multicellular glands and dip inwards between them. 



Fig. 10. — A portion of the epithelium of the atrial duct. m. Muscles. 

 b. V. Blood-vessel. 



Fig. 11.— a portion of the glandular region of the atrial duct (see Fig. 8, 

 gl.). ep. Epithelium, gl. Gland-cells, m. Muscles. 



Fig. 12. — Transverse section of sperm-duct. ep. Large striated epithelial 

 cells, mus. Muscles, spoa. Spermatozoa. 



Fig. 13. — Longitudinal section of the copulatory sac, showing its constric- 

 tion by Septum vii/viii, and the entrance into it of the spermathecal duct 

 {spth. duct), ep. Epithelium, mus. Muscular coat. 



Fig. 14. — A portion of the epithelium of the copulatory sac. 



Fig. 15. — Section of spermathecal duct, to show the very thick coat of 

 circularly disposed muscles. 



Fig. 16. — A series of diagrammatic sections illustrating my view as to the 

 development of the prostate in earthworms from the condition in Tubifex. 

 The lining epithelium of the atrium is represented as consisting of cubical 

 cells, the muscular coat by thick lines, the ccelomic epithelium by interrupted 

 lines. 



