Which of the following statements is incorrect about the nervous system of earthworm ?

Options

A. Nervous system is basically representes by ganglia arranged on ventral nerve cord
B. In `3^(rd)` and `4^(th)` segment, the nerve cord bifurcates and joins the cerebral ganglia dorsally to form a nerve ring
C. The cerebral ganglia along with other nerves in the ring integrate sensory input as well as command muscular responses of the body
D. none of these

Answer

To determine which statement is incorrect about the nervous system of the earthworm, we need to analyze the structure and function of its nervous system based on the information provided.

### Step-by-Step Solution:

1. **Understand the Nervous System Structure**:
- The earthworm belongs to the phylum Annelida, which is characterized by having a ventral nerve cord.
- The nervous system of the earthworm consists of a paired ventral nerve cord with ganglia.

2. **Identify the Ganglia Arrangement**:
- The ganglia are arranged segmentally along the ventral nerve cord. This means that each segment of the earthworm has a corresponding ganglion.

3. **Nerve Cord Bifurcation**:
- The ventral nerve cord bifurcates (divides) at the third and fourth segments of the earthworm. This bifurcation is significant as it connects to the cerebral ganglia.

4. **Formation of the Nerve Ring**:
- After bifurcation, the nerve cord encircles the pharynx and joins the cerebral ganglia dorsally, forming a nerve ring. This structure is crucial for integrating sensory information.

5. **Function of the Cerebral Ganglia and Nerve Ring**:
- The cerebral ganglia and nerve ring work together to process sensory input and command muscular responses, allowing the earthworm to react to stimuli.

6. **Evaluate the Statements**:
- Now, we evaluate the statements provided in the question.
- If all statements accurately describe the nervous system of the earthworm, then there is no incorrect statement.

7. **Conclusion**:
- Based on the information, if all the statements about the nervous system of the earthworm are true, then the answer to the question is that there is no incorrect statement.

### Final Answer:
None of the statements about the nervous system of the earthworm are incorrect.

---