Polymorphism:
Actually the Greek word polymorphism means (Poly – many; morpi – form) occurrences of more than one form of zooids in a single species. So, polymorphism can be defined as the occurrence of several different types of individuals (Zooids) in more than one form to perform various functions showing excellent cases of division of labor among different forms which are originally connected and of the same species.
Basic form of Polymorphism:
Though from simple to very complex polymorphism occurs in Cnidarian, the basic forms are represented by two types of zooids known as polyp and medusa.
Class Hydrozoa: Polypoid and medusoid forms occur.
Class Scyphozoa: Modusoid forms are predominant.
Class Actinozoa: Polypoid forms are found.