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- 



lyph 



neph 



hep 



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 ; ccel. ccelome ; 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. riephrostome ; n. co. nerve cord ; set. setas ; sub. n. vess. sub- neural 

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

 and Haswell's Zoology, aiter 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- 



