The members of this phylum are called as flatworms.
Unique features of phylum Platyhelminthes:
1. Body shape: Body of these animals is dorsoventrally flattened.
2. Coelom: They are acoelomates.
3. Germ layers: Platyhelminthes are triploblastic.
4. Body organization: They show organ-system grade of organization.
5. Forms: Most of them are endoparasites and few are free-living. Parasitic forms have hooks and suckers for attachment to the hosts’ body. In parasitic forms, body is covered by cuticle and in free-living forms it is covered by cilia.
6. Digestive system: Parasitic forms generally lack digestive system. In free-living forms, the digestive system is incomplete.
7. Body plan: They show blind-sac body plan.
8. Excretion and osmoregulation: It occurs by flame cells or protonephridia.
9. Reproduction: They are mostly hermaphrodite (bisexual).
10. Self-fertilization: Few animals show high power of regeneration and show polyembryony. e.g. Planaria, Taenia (Tapeworm), Fasciola (Liver fluke) are included in this phylum.
