198 



COMPARATIVE ANATOMY 



CHAP. 



daeum, rd) stretches to the most anterior end of the body, to emerge 

 generally separately from the oral aperture in front of and above it. 

 The whole proboscidal apparatus is entirely separate from the intestinal 

 canal. The rhynchodreum thus leads through the proboscidal aperture 



FIG. 131. Diagrammatic representation of the proboscidal apparatus of the Nemertina. .4, 

 Proboscis withdrawn. /;, Proboscis protruded. ?-, Proboscis ; rs, proboscis sheath ; rsh, cavity of 

 the latter ; st, stylet ; gel, poison gland ; rm, retractor muscle ; rrf, rhynchodseum. 



into the central cavity of the proboscis which closes blindly behind. 

 The wall of the long proboscis is extremely muscular, the arrangement 

 of the fibres being occasionally very complicated. It is internally 

 lined with epithelium which is continued on to the rhynchodaeuni, 



