Stomochord is a rudimentary structure present in the collar region. It is found in

Options

A. chordates
B. cephalochodates
C. urochordates
D. hemichordates

Answer

### Step-by-Step Solution:

1. **Understanding the Term "Stomochord":**
- The stomochord is a rudimentary structure that is found in certain organisms. It is specifically noted for its presence in the collar region of these organisms.

2. **Identifying the Group of Organisms:**
- Stomochord is found in hemichordates, a group of marine animals that are closely related to chordates.

3. **Structure and Function of Stomochord:**
- The stomochord is a tubular structure that arises during the embryonic development of hemichordates.
- In adult hemichordates, the stomochord extends dorsally from the pharynx into the proboscis, which is the part of the organism that communicates with the oral cavity.

4. **Composition of Stomochord:**
- The walls of the stomochord are primarily composed of epithelial cells.
- Additionally, ciliated and glandular cells are also present in its structure, contributing to its function.

5. **Conclusion:**
- Based on the information gathered, the stomochord is specifically found in hemichordates.

### Final Answer:
Stomochord is a rudimentary structure present in the collar region and is found in **hemichordates**.

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