Define polymerphism. Name one ceolenterate showing polymerphism.

Explanation

### Step-by-Step Solution:

1. **Definition of Polymorphism**:
- Polymorphism refers to the phenomenon where organisms exhibit two or more distinct forms or morphs within the same species. This means that an organism can exist in different shapes or structures depending on certain conditions or stages in its life cycle.

2. **Examples of Organisms Showing Polymorphism**:
- In the context of coelenterates (also known as cnidarians), one of the most notable examples of polymorphism is found in the organism **Obelia**.

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