Paramecia are single-celled organisms, meaning they are eukaryotic cells.

Here's why:

* Eukaryotic cells have a true nucleus that contains their genetic material (DNA). This is in contrast to prokaryotic cells (like bacteria) which lack a nucleus.

* Paramecia are complex organisms with specialized structures within their single cell, such as cilia for movement, contractile vacuoles for water regulation, and food vacuoles for digestion. These structures are characteristic of eukaryotic cells.

So, while a paramecium is a single cell, it's a complex, eukaryotic cell with many specialized features.