1. They are diploblastic animals. That is, their cells have two cell layers called ectoderm and endoderm.
2. Between the ectoderm and endoderm is an acellular layer called mesoglia.
3. Their body shape is filamentous, tubular and umbellate.
4. The body consists of nidoblast cells, which bear nematocysts.
5. There is a body cavity called gastrovascular or cilantern. The cilianteron is called the alimentary canal. It acts as the mouth and anus and participates in digestion and transport.
6. Cellular and organelle division of labor is seen.
7. The life cycle includes genetics, metagenesis and polymorphism.
8. In the life cycle there are stationary polyp dasa and active medusa dasa.
9. Body does not have organ system, respiratory system and circulatory system. The nervous system is underdeveloped.
10. They are multicellular, asymmetrical and headless.
11. Food material is digested extracellularly and intracellularly.
12. Respiration occurs through ciliated planula larvae.
13. Twenty species of Nidaria are freshwater. The remaining Nidaria are marine.
Characteristics Key words to remember: diploblastic, mesoglia, nidoblast, coelenteron, division of labor, metagenesis, polymorphism, polyp, medusa]