Cocoon is secreted by ……………… .

Explanation

**Step-by-Step Solution:**

1. **Understanding the Cocoon**: A cocoon is a protective casing that is secreted by certain organisms, including earthworms, during their reproductive process.

2. **Identifying the Source**: In earthworms, both male and female reproductive structures are present. The cocoon is specifically secreted by the female reproductive structure.

3. **Location of Secretion**: The cocoon is secreted from a specific area in the earthworm known as the "clitellum." This structure is located in segments 14, 15, and 16 of the earthworm.

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