Which of the following coelenterate exist in both forms polyp and medusa and exhibit metagenesis.

Options

A. Hydra
B. Adamsia
C. Obelia
D. Gorgonia

Answer

To solve the question regarding which coelenterate exists in both polyp and medusa forms and exhibits metagenesis, we can follow these steps:

### Step 1: Understand the Terms
- **Coelenterates**: These are a group of animals that include jellyfish, corals, and sea anemones, characterized by a simple body structure and a single opening surrounded by tentacles.
- **Polyp and Medusa Forms**: Coelenterates can exist in two forms:
- **Polyp**: A cylindrical form that is usually sessile (attached to a surface).
- **Medusa**: A free-swimming form that is typically umbrella-shaped.
- **Metagenesis**: This refers to a reproductive cycle that alternates between asexual and sexual generations.

### Step 2: Identify the Options
- The question provides several options (not listed here) to choose from. We need to identify which of these options are coelenterates that can exist in both forms and exhibit metagenesis.

### Step 3: Analyze the Options
- **Obelia**: This is a colonial coelenterate that exhibits both polyp and medusa forms and undergoes metagenesis. The polyp form reproduces asexually, while the medusa form reproduces sexually.
- **Gorgonia**: This is a type of sea fan coral that primarily exists in the polyp form and does not exhibit metagenesis.

### Step 4: Conclusion
Based on the analysis, the correct answer to the question is **Obelia**, as it is the only option that fulfills the criteria of existing in both polyp and medusa forms and exhibiting metagenesis.

### Final Answer
The correct answer is **Obelia**.

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