The free swimming larva of coelenterates is

Options

A. Planula
B. Cydippid
C. Parenchymula
D. Amphiblastula

Explanation

**Step-by-Step Solution:**

1. **Understanding Coelenterates**: Coelenterates, also known as cnidarians, include organisms such as jellyfish, corals, and sea anemones. They exhibit two main body forms: the polyp and the medusa.

2. **Identifying Larval Forms**: In the life cycle of coelenterates, larvae are produced from both the medusa and polyp forms. These larvae are typically free-swimming.

3. **Characteristics of the Larva**: The free-swimming larva of coelenterates is characterized by:
- Having cilia for movement.
- Being cylindrical in shape.
- Being free-living.

4. **Naming the Larva**: The specific name for the free-swimming larva of coelenterates is the "planula." This larva is formed after fertilization and is an important stage in the life cycle of cnidarians.

5. **Evaluating Options**:
- The first option states that the free-swimming larva of coelenterates is a planula, which is correct.
- The other options (cytid, parenchymula, and amphiblastula) refer to larvae of different organisms (e.g., pinophora and sponges) and are therefore incorrect.

6. **Conclusion**: The correct answer to the question is that the free-swimming larva of coelenterates is called a planula.

**Final Answer**: The free swimming larva of coelenterates is called a planula.

---