In which phylum nerve cells are found but nerves are absent

Options

A. Porifera
B. Coelenterata
C. Platyhelminthes
D. Nametohelminthes

Answer

To answer the question "In which phylum are nerve cells found but nerves are absent?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: We need to identify a phylum where nerve cells exist, but organized structures known as nerves do not.

2. **Reviewing the Options**:
- **a. Porifera**: Members of this phylum (sponges) do not have a nervous system at all; they lack nerve cells.
- **b. Cnidaria (Silentrata)**: This phylum includes organisms like jellyfish and corals. They have nerve cells but do not have a centralized nervous system or organized nerves.
- **c. Platyhelminthes**: This phylum (flatworms) has a more developed nervous system with nerve cords and ganglia.
- **d. Nematoda (Nematohelminthes)**: This phylum (roundworms) also has a nervous system with organized nerves.

3. **Analyzing Cnidaria**: In Cnidaria, the nervous system is a simple nerve net, and while they have nerve cells (neurons), they do not have true nerves as seen in more complex organisms.

4. **Conclusion**: Based on the analysis, the phylum that contains nerve cells but lacks organized nerves is **Cnidaria (Silentrata)**.

5. **Final Answer**: The answer to the question is **Option B: Cnidaria (Silentrata)**.