OELHELMINTHES 



201 



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

 ncmatodes and annelids, is not settled. The body muscles are 

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

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





FIG. 240. -Section of A scaris lumbricoides through the pharyngeal bulb; beside it 

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

 itudinal muscle; n, nucleus of muscle cell; p, muscle cell; 5, lateral line; v, ventral line: 

 w, excretory canal. 



0... 



* -m : 



^tlllJPt 



5 



more 



FIG. 241. Transverse section of Sagitta bipuncta'.a and a bit of the body wall m^ic 

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

 e, epidermis; m, somatic mesoderm (muscles and epithelium); o, 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 



