PHYLUM PLATYHELMINTHES 

 prop ap 



M7 



brob'- 



brob 



Tetr.mus 



dcsv&& 



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

 accessory stylet ; cer. g, brain : cil.gr, ciliated groove ; dors. 7-es, dorsal vessel ; 

 lat. tie, lateral nen r e ; Int. ves, lateral vessel; neph, nephridium ; op. neph, 

 nephridial aperture ; prob 1 , eversible part of proboscis : prob-, non-eversible part 

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

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



