QtLYCEBIDM 



473 



same relations as have the muscles and neural sheath, including the notochord, of a 

 vertebrate." : The alimentary canal has a powerful layer of longitudinal muscles 

 externally, and in some species (e.g., G. lapidum) this layer holds two large vessels (dorsal 

 and ventral). 



Gills absent or present, sometimes retractile. The large nerve-cords (e.g., in G. lapi- 



Flg. 91. — Diagrammatic reconstruction of the nephridial complex of Glycera siphonostoma, showing the nephridial 

 sac (empty), the ciliated organ, and the nephridium. co. Ciliated organ, ns. Nephridial sac. si. Soleno- 

 cytes. cc. Chambered caecum, nd. Nephridial duct. (Goodrich.) 



dam, Fig. 90) are wedged in a hypodermic area between the large ventral muscles, which 

 touch at their dorsal edges so as to form an arch over the nerves. The external circular 

 muscular layer ceases before reaching the nerve-area, so that externally are only hypo- 

 derm and the specially thickened cuticle. The oblique muscles, attached above the 

 cords, are slightly developed. Segmental organs (Fig. 91) blind internally, opening by a 



F IG . 92.— Diagrammatic reconstruction of a portion of the nephridium of Glycera siphonostoma, cut so as to show the 

 course of the canals. The inner surface would be applied to the wall of the nephridial sac. cb. Cell-body 

 (solenocyte). ml. Main branch. /. Flagellum, continued into the chamber, t. Tube with cilium in it. 

 nd. Nephridial duct. ch. Chamber, on, s. Outer surface, in. s. Inner surface. (Goodrich.) 



pore on the ventral surface. Canal, which branches, passes inward and forward 

 through the next septum to the genital funnel, which is known to accumulate waste 

 products, and then spreads over the nephridial sac (or pouch of ccelomic epithelium). 

 Solenocytes arranged in small groups (Goodrich). Exit of genital products not known. 

 1 Ray Lankester, ' Ann. Nat. Hist./ ser. 4, vol. xi, p. 92. 



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