Which one of the following animals possesses nerve cells but no nerves?

Options

A. Hydra
B. Tapeworm
C. Earthworm
D. Frog's tadpole

Explanation

To determine which animal possesses nerve cells but no nerves, we can analyze the options provided:

1. **Hydra**: Hydra is a simple organism that has nerve cells, also known as ganglion cells. These cells can be small or elongated and have one or more processes. Hydra does not have a centralized nervous system or well-developed nerves. Instead, it has a nerve net, which is a decentralized network of nerve cells spread throughout its body, allowing for basic sensory responses such as touch and chemical detection.

2. **Tapeworm**: Tapeworms are more complex than hydra and possess a nervous system with a more organized structure, including nerves.

3. **Earthworm (Archworm)**: Earthworms have a well-defined nervous system with a ventral nerve cord and segmental ganglia, indicating the presence of nerves.

4. **Fractastport**: This option seems to be a typographical error or a misrepresentation of a known organism. Assuming it refers to a known organism, it would likely also have a more developed nervous system.

Based on this analysis, the only organism that possesses nerve cells but lacks a structured nervous system with nerves is:

**Answer: Hydra**

### Step-by-Step Solution:
1. **Identify the Options**: Look at the animals listed: Hydra, Tapeworm, Earthworm, and Fractastport.
2. **Examine Hydra**: Understand that Hydra has nerve cells (ganglion cells) but lacks a centralized nervous system and structured nerves.
3. **Analyze Other Options**: Review the characteristics of Tapeworm, Earthworm, and Fractastport to confirm they have developed nervous systems with nerves.
4. **Conclude**: Since Hydra is the only option that fits the criteria of having nerve cells but no nerves, it is the correct answer.