330 



THE EARTHWORM 



CHAP. 



a feather on a central axis (long. mus). Finally, within 

 the muscular layer and lining the ccelome is a thin 

 peritoneal membrane (parietal layer, compare p. 26), on 



dors.v 



typh 



neph 



nephrost 



n.co 



set 



FIG. 81. Lumbricus, semidiagrammatic transverse section of the middle region of 



the body, (x about 18.) 



circ. mus. layer of circular muscular fibres ; cod. coelome ; cut. cuticle ; dors. v. 

 dorsal vessel ; epid. epiderm ; ext. neph. nephridiopore ; hep. layer of yellow 

 cells ; long. mus. longitudinal muscles ; neph. nephridium (shown entire) : 

 nephrost. nephrostome ; n. co. nerve cord ; set. setae ; sub. n. vess. sub- neural 

 vessel ; typh. typhlosole ; vent. v. ventral (sub-intestinal) vessel. (From Parker 

 and Haswell's Zoology, after Marshall and Hurst.) 



the inner surface of which is a very thin layer of cells, 

 the ccelomic epithelium. 



A transverse section of the intestine shows an inner 

 layer of ciliated, columnar enteric epithelium (compare 

 p. 109), a very thin middle layer composed of muscle- 



