Q.Draw neat labelled diagram: Aurelia

Cnidaria (Greek knide, sting), formerly Coelenterata, are aquatic animals — sessile or free-swimming, solitary or colonial — that are radially symmetrical except for the bilaterally symmetrical sea anemones. The name comes from cnidocytes (cnidoblasts), stinging cells bearing a nematocyst, used for anchorage, defence, and prey capture.

Cnidarians are the first phylum on the classification tree to show tissue-level organisation, remaining diploblastic. A single central cavity, the coelenteron, handles both digestion and circulation, opening to the outside through one mouth (hypostome) used for both ingestion and egestion; digestion is both extracellular and intracellular. The nervous system is a primitive, diffused nerve net. …