This document summarizes several phyla of invertebrate worms, including their defining characteristics, anatomy, life cycles, and means of reproduction and nutrition. It covers the phyla Platyhelminthes (flatworms), Nemertea (ribbon worms), and Gnathostomulida (jaw worms). Key details provided include the classes that make up Platyhelminthes (turbellarians, trematodes, monogeneans, cestodes), their digestive and nervous systems, and complex parasitic life cycles involving multiple hosts.