Vorticella dividing.

Vorticella is a single cell in the subclass Peritricha. Vorticella features a characteristic feeding current (or vortex, hence the name) created by cilia encompassing the mouth (cytostome), as well as a long, contractile stalk which allows the cell to contract like a spring when disturbed. I was lucky enough to find a Vorticella producing offspring, as you can see in the attached photomicrograph (a photograph of something microscopic).