Read the given statements and select the incorrect one.

Options

A. In Hydra, all neurons are similar and join to form a nerve cell.
B. In earthworms, nervous system consists of a dorsal nerve cord, paired ganglia and segmental nerves.
C. Brain is present in insects.
D. Planaria has two nerve cords that join to form rudimentary brain.

Explanation

To determine the incorrect statement among the given options, let's analyze each statement one by one:

1. **Statement 1**: "In Hydra, all neurons are similar and joined to form a nerve cell."
- **Analysis**: This statement is generally correct. Hydra has a simple nerve net where all neurons are similar in structure and function, and they are interconnected, forming a diffuse nerve net rather than a centralized nerve cell.

2. **Statement 2**: "In Earthworm, the nervous system consists of a dorsal nerve cord, paired ganglia, and segmental nerves."
- **Analysis**: This statement is incorrect. The earthworm has a ventral nerve cord, not a dorsal one. The ventral nerve cord runs along the belly side of the earthworm, and it is segmented, with paired ganglia in each segment.

3. **Statement 3**: "Brain is present in insects."
- **Analysis**: This statement is correct. Insects, which belong to the phylum Arthropoda, have a well-developed brain and a complex nervous system.

4. **Statement 4**: "Planaria has two nerve cords that join to form a rudimentary brain."
- **Analysis**: This statement is also correct. Planaria has a simple nervous system with two longitudinal nerve cords that connect to a pair of cerebral ganglia, forming a rudimentary brain.

Based on the analysis, the incorrect statement is **Statement 2**.

### Final Answer:
The incorrect statement is: **"In Earthworm, the nervous system consists of a dorsal nerve cord, paired ganglia, and segmental nerves."** (This should be a ventral nerve cord.)

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