CHAPTER 33 INVERTEBRATES OUTLINE I. The Parazoa A. Phylum Porifera: sponges are sessile with porous bodies and choanocytes II. The Radiata A. Phylum Cnidaria: cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes B. Phylum Ctenophora: comb jellies possess rows of ciliary plates and adhesive colloblasts III. The Acoelomates A. Phylum Platyhelminthes: flatworms are dorsoventrally flattened acoelomates IV. The Pseudocoelomates A. Phylum Rotifera: rotifers have jaws and a crown of cilia B. Phylum Nematoda: roundworms are unsegmented and cylindrical with tapered ends V. The Coelomates: Protostomes A. Phylum Nemertea: The phylogenetic position of proboscis worms is uncertain B. The lophophorate phyla: bryozoans, phoronids, and brachiopods have ciliated