1. In the embryonic stage, the hydra body is divided into ectoderm and endoderm layers. In mature animals, ectoderm transforms into epidermis and endoderm transforms into gastrodermis.
2. In the center of the body is the cilantern or gastrovascular cavity. It is exposed to the outside through the mouth.
3. The body wall consists of interstitial cells. It can be transformed into any other cell. Dr. Siddiq Publications
4. Epidermis consists of nidoblast or nidocyte cells. Nidocyte cells contain nematocysts.
5. Cellular division of labor can be seen.
Hydra is included in the Cnidaria phylum due to the above characteristics.