POLYMORPHISM Definition One of the important characters of Eumetazoa is the division of labour. In the vast majority, i.e., from flat worms to chordates, the division of labour involves the assignment of different functions to different parts or organs of the individual. In coelenterates, low organization and lack of organs do not permit any great degree of specialization for different functions within the limits of an individual. Therefore, in these animals the different vital functions are assigned to different individuals. This form of the division of labour is known as polymorphism. Polymorphism is, thus, the phenomenon of occurrence of an animal in more than one morphological and functional form. The individuals of polymorphic animals are known as the zooids or persons. 2. Grades Some coelenterates possess only two types of zooids, others have three types, and still others several types. These forms are respectively described as dimorphic, trimorphic and polymorphic. There ...
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