Regeneration was first discovered in

Options

A. Planaria
B. Hydra
C. Sponges
D. Salamander

Answer

**Step-by-Step Solution:**

1. **Understanding Regeneration**: Regeneration is the biological process by which certain organisms can replace or restore lost or amputated body parts. This ability varies among different species.

2. **Identifying Organisms Known for Regeneration**: Several organisms are known for their regenerative capabilities, including Planaria, Hydra, Sponges, and Salamanders.

3. **Historical Context**: The question asks where regeneration was first discovered. This implies that we need to identify the organism that was first studied or recognized for its regenerative abilities.

4. **Researching the Discovery**: The first documented study of regeneration was conducted by Abraham Trembley in the 18th century. He experimented with Hydra, a freshwater polyp, to observe its regenerative properties.

5. **Trembley's Experiment**: Trembley cut the Hydra into pieces and observed that each piece could regenerate into a complete organism. This led him to conclude that Hydra had remarkable regenerative capabilities.

6. **Conclusion**: Based on historical records, the organism in which regeneration was first discovered is Hydra.

7. **Final Answer**: Therefore, the correct answer to the question "Regeneration was first discovered in" is **Hydra**.

---