Which of the following animals is devoid of notochord and nerve cord in its adult stage ?

Options

A. Herdmania ( Ascidian )
B. Branchiostoma (amphioxus )
C. Assymetron
D. All of the above

Answer

To solve the question "Which of the following animals is devoid of notochord and nerve cord in its adult stage?", we need to analyze the options provided and understand the characteristics of each animal mentioned.

### Step-by-Step Solution:

1. **Understand the Terms**:
- **Notochord**: A flexible rod-like structure that provides support in the embryonic stage of chordates.
- **Nerve Cord**: A structure that develops into the central nervous system in chordates.

2. **Identify the Options**:
- a. Herdmania (Ischindia)
- b. Branchiostoma (Amphioxus)
- c. Asymmetron
- d. All of the above

3. **Analyze Each Option**:
- **Herdmania (Ischindia)**: This is a type of tunicate (sea squirt) that has a larval stage with a notochord and nerve cord. However, in the adult stage, it undergoes retrogressive metamorphosis and loses these structures, becoming a sessile organism.
- **Branchiostoma (Amphioxus)**: This organism retains the notochord and nerve cord throughout its life, including the adult stage. It is a representative of cephalochordates.
- **Asymmetron**: Similar to Branchiostoma, Asymmetron retains its notochord and nerve cord in the adult stage.

4. **Conclusion**:
- Among the options, only **Herdmania (Ischindia)** is devoid of notochord and nerve cord in its adult stage. Therefore, the correct answer is **option A**.

### Final Answer:
**Option A: Herdmania (Ischindia)** is the animal that is devoid of notochord and nerve cord in its adult stage.

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