In which of the following animals notochord is not present

Options

A. Adult tunicate
B. Herdmania
C. Myxine
D. Balanoglossus

Answer

To determine which animal does not possess a notochord, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Notochord**:
- The notochord is a rod-like structure found in chordates, located between the nerve cord and the gut. It serves as a support structure and a point for muscle attachment.

2. **Identify the Groups of Chordates**:
- Chordates are divided into three main groups:
- **Urochordata**: Notochord is present only in the larval stage.
- **Cephalochordata**: Notochord is present in both larvae and adults.
- **Vertebrata**: Notochord is present during the embryonic stage but is replaced by the vertebral column in adults.

3. **Analyze the Options Given**:
- The options provided include:
- Adult tunicates (Urochordata)
- Herdmania (Urochordata)
- Myxine (Vertebrata)
- Balanoglossus (Hemichordata)

4. **Evaluate Each Option**:
- **Adult Tunicates**: As adults, they do not possess a notochord.
- **Herdmania**: Similar to adult tunicates, they also do not have a notochord in the adult stage.
- **Myxine**: This is a jawless vertebrate that has a notochord during its embryonic stage.
- **Balanoglossus**: Belongs to Hemichordata, which has a structure similar to a notochord.

5. **Conclusion**:
- Based on the analysis, the organism that does not have a notochord in its adult form is the **Adult Tunicate**. Therefore, the answer to the question is **Adult Tunicates**.

### Final Answer:
**Adult Tunicates**

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