……………. maintain a water currect in the sponges.

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Sponges**: Sponges are simple aquatic animals that belong to the phylum Porifera. They are characterized by their porous bodies and lack of true tissues and organs.

2. **Cellular Structure**: The body of a sponge is made up of a variety of cells, which are organized in a loose aggregation. Unlike more complex animals, sponges do not have specialized tissues or organs.

3. **Identifying the Key Cells**: Within the sponge, there are specific cells responsible for maintaining water flow. These cells are known as choanocytes.

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