Define the following :
Notochord.

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Notochord**: The notochord is a long, rod-like structure found in the embryos of all chordates.

2. **Composition**: It is primarily composed of cartilage, which provides flexibility and support.

3. **Function**: The notochord serves as a structural support system and plays a crucial role in the development of the nervous system.

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