Chapter 6 Flatworms Turbellarians and Nemertea

The turbellarian flatworms are basal among the Bilateria, showing such presumably primitive features as an incomplete gut—with only a mouth and no anus—and an acoelomate body structure. Most turbellarians are members of the phylum Platyhelminthes, which also comprises the major parasitic groups of flatworms—namely the Monogenea (ectoparasitic flukes), Cestoidea (tapeworms), and Trematoda (endoparasitic flukes)—and which is considered part of …