Platyhelminthes (phylum Platyhelminthes), also known as flatworms, are bilaterian, unsegmented and soft-bodied invertebrates. Platyhelminthes are hermaphroditic organisms with internal fertilization. In addition, this group shows a series of characteristics including 1-a ladder-like nervous system, 2-presence of parenchyma in the body cavity, and 3-flame cells, i.e., specialized excretory cells that function like a kidney. Platyhelminthes can be divided into three groups: Turbellaria (generally found in freshwater), Trematoda (generally parasitic), and Cercomeromorpha (exclusively parasitic).
