CCELHELMINTHES 



261 



intestine; but whether this ccElom be homologous in different groups, e.g., 

 nematodes and annehds, is not settled. The body muscles are 

 developed from the outer (parietal) epithelial wall of the ccelom 

 and hence are 'epithelial muscle cells' (figs. 240, 241). The pro- 



FlG. 240. — Section of Ascaris lumbricoides through the pharj'ngeal bulb; beside it 

 a bit of the body wall more enlarged, c, cuticle; d, dorsal line; h, hypodermis; m, long- 

 itudinal muscle; n, nucleus of muscle cell; p, muscle cell; s, lateral line; v, ventral line; 

 ui, excretory canal. 



Fig. 241. — Transverse section of Sagilta bipunctala and a bit of the body wall more 

 enlarged (after O. Hertwig). c, ccelom; dd, entoderm; df, splanchnic mesothelium; 

 e, epjidermis; m, somatic mesoderm (muscles and epitheUum); 0, ovary. 



tonephridia of the larval stages are replaced by nephridia (fig. 71), 

 connecting the body cavity with the outer world. Internally they begin 

 with a ciliated funnel, the nephrostome, and continue as long coiled tubes, 

 expanding just before the outer end to a kind of bladder. The gonads 



