PHYLUM PLATYHELMINTHES 



M7 



brob'- 



brob' 



TeZr.nuts 



— dors ves 



| £^A neph 



f- dors ve& 



Fig. 80. — Tetrastemma. General view of the internal organs, an, anus; ac. si, 

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

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

 nephridial aperture ; prod 1 , eversible part of proboscis ; prod 2 , non-eversible part 

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

 retractor muscle of the proboscis ; st, stylet, (From Hatschek's Lthrbuck.) 



