TKANSVEESE SECTIONS 



71 



near their bases. Many of these cells have the 

 character of 'goblet cells,' being distended by a 

 granular secretion formed within them ; other cells 

 lying between these are extremely slender. In the 

 clitellum the epidermis is greatly thickened, and 

 blood-vessels penetrate between the cells. 



CM 



LM 



FIG. 18. Lumbricus terrestris. A diagrammatic transverse section 

 through the middle of the body. On the left side of the figure a 

 nephridium is shown, and on the right side the setae. The septa 

 are not shown, and parts only of the circulatory system are repre- 

 sented. (A. M. M. 



A, cuticle. B, epidermis. C, coelom. CM, layer of circular muscles. 

 D, seta. DV, dorsal vessel. E, cavity of intestine. 3P, cavity of typhlosole, 

 filled with 'hepatic' cells. Q-, epithelium of intestine. H, 'hepatic' cells 

 clothing intestine. I, ventral nerve-cord. J, nerve. K, ' giant fibres.' t, 

 ciliated funnel of nephridium, opening into coelom. LM, layer of longitudinal 

 muscles. M, the point where the nephridium perforates the septum 'between 

 two segments : between the two cut ends a considerable length of very fine 

 tube lies, which is not shown in the figure. U, the first or middle loop of the 

 nephridium. O, the second or inner loop of the nephridium. P, the third or 

 outer loop of the nephridium. R, external aperture of the nephridium. 

 SV, subneural vessel. V, lateral vessel. W, ventral vessel. 



