Brain coral belongs to this phylum.

Characteristics of members belonging to phylum Cnidaria: 

1. Habitat: They are aquatic, mostly marine and few of them are fresh – water forms. 

2. Forms: They are sessile or free swimming. 

3. Cnidoblasts: Presence of cnidoblasts or stinging cells are present on the tentacles for anchorage, offence and defence.

4. Body Symmetry: They have radially symmetrical body. 

5. Germ layer: They are diploblastic. 

6. Body cavity: Cnidarians have a central cavity called coelenteron or gastrovascular cavity, which helps in digestion and circulation. They have blind-sac body plan i.e., single pore opening to the exterior in the digestive system. 

7. Body form: Members of this phylum exhibit two body forms. The cylindrical form, known as polyp e.g. Hydra and the umbrella – like form (.Aurelia – jelly fish) is known as medusa. 

8. Digestion: They have extracellular and intracellular digestion. 

9. Reproduction: Cnidarians reproduce asexually and sexually. Asexual reproduction takes place by budding and regeneration. Sexual reproduction takes place gamete formation. 

10. They exhibit metagenesis i.e. alternation of polypoid generation with medusoid generation. Polyps produce medusae asexually and medusae produce polyps sexually, e.g. Obelia 

11. e.g. Hydra, Aurelia (Jellyfish), Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Diploria (Brain coral), Gorgonia (sea fan).