Nerve cells are not found in

Options

A. Platyhelminthes
B. Coelenterata
C. Sponges
D. Echinodermata.

Answer

### Step-by-Step Solution

1. **Understanding the Question**: The question asks where nerve cells are not found among the given options: pletia elementae, coelenterata, tratra, sponges, and echinodermata.

2. **Identifying the Options**: The options provided are:
- Pletia elementae
- Coelenterata
- Tratra
- Sponges
- Echinodermata

3. **Analyzing Each Option**:
- **Pletia Elementae**: This is likely a misspelling or misinterpretation of "Platyhelminthes", which do have nerve cells.
- **Coelenterata**: This group, which includes cnidarians like jellyfish and corals, also possesses nerve cells.
- **Tratra**: This option is unclear but seems to be a typographical error. If it refers to "Trichoplax" or similar, these organisms do have some form of nerve cells.
- **Sponges**: Sponges belong to the phylum Porifera and are known for lacking true nerve cells. They are primitive multicellular organisms that do not have a nervous system.
- **Echinodermata**: This group includes starfish and sea urchins, which do have a decentralized nerve net.

4. **Conclusion**: Based on the analysis, the correct answer is **sponges**, as they do not contain nerve cells.

### Final Answer:
Nerve cells are not found in **sponges**.

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