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MANUAL OF ELEMENTARY ZOOLOGY 



body-wall, where they are attached opposite the grooves on 

 the surface of the body. The ccelom contains a fluid, and 

 in this float the leucocytes already mentioned, by which 

 small parasites are surrounded and destroyed, both within 

 and without the body. The body-wall is covered by the 



Fig. 136. 



-A transverse section through an earthworm in the region 

 of the intestine. 



cce., Ccelom ; c.m.b., circular muscle of body-wall ; c.m.g., circular muscle of gut ; 

 cu. , cuticle; d.b.v., dorsal blood vessel ; d.p., dorsal pore ; cfi., epidermis ; end., 

 endoderm ; g.f., giant fibres ; l.m.b., longitudinal muscle of body-wall; l.vig. t 

 longitudinal muscle of gut ; Ln.zi., lateral neural vessel ; «., nerves ; H.C., nerve 

 cord ; nph., nephridium ; p.e.b., peritoneal epithelium of body-wall ; set., seta ; 

 s.i.v., subintestinal blood vessel ; s.n.v., subneural blood vessel ; s.s. t seta sac ; 

 ty., typhlosole ; y.c, yellow cells. Seta sac muscles are shown but not lettered. 



cuticle. Under this lies the epidermis, an epithelium con- 

 sisting of columnar cells, many of which are glandular or 

 sensory, with small cells between their bases. The cuticle 

 is perforated by a pore over each gland cell. The 

 epidermis of the clitellum consists of several layers of gland 

 cells. Below the epidermis is a circular layer of muscle, 



