PHYLUM PLATYHELMINTHES 

 ftrop. afa 



ciigr 



Irrob 



retr.mue 



FIG. Bo. Tetrastemma. General view of the internal organs, an, anus: <:. st, 

 accessory stylet ; cer. g, brain : cil.gr, ciliated groove ; dors, ves, dorsal vessel ; 

 lat. ne, lateral nerve; lat. ves, lateral vessel; neph, nephridium ; op. neph, 

 nephridial aperture ; profr, eversible part of proboscis : prob*, non-eversible part 

 of proboscis; prob. ap, aperture for the protrusion of the proboscis; retr. mus, 

 retractor muscle of the proboscis ; st, stylet. (From Hatschek's Lthrbuch,} 



