Flatworms are eukaryotes, meaning their cells have a membrane-bound nucleus that contains their genetic material (DNA).

Here's why:

* Eukaryotic Cells: All eukaryotic organisms, which includes animals like flatworms, have cells with a nucleus. This is what distinguishes them from prokaryotes (like bacteria) which lack a nucleus.

* DNA Storage: The nucleus is crucial for storing and protecting the DNA that determines the organism's traits and functions.

* Cellular Processes: The nucleus also plays a role in regulating cell division and other essential cellular processes.

So, flatworms, like all other animals, have nuclei within their cells.