Polyp and medusa are the asexual and sexual phase present respectively in coelenterates. The members of different classes can be differentiated by the presence or absence of these stages. Aurelia (jelly fish) belongs to class-Scyphozoa, in which medusoid phase is dominant and polypoid phase absent. Hydra, Obelia, Physalia are the members of class- Hydrozoa in which, both medusoid and polypoid stages are present. Metridium, Tubipora etc., belong to class- Anthozoa, with all polyps but no medusae.