Vorticella (single-celled)

Vorticella
The 'bell' is up to 150 µm, with stalk up to 1 mm.
You can find them attached to algae and plants etc.

Vorticella are one of the peritrich protozoa. Although solitary, they often occur in groups to form a tiny jelly-like mass just visible to the naked eye. Their stalks contract like a spring (they remind me of a slinky). Some similar types e.g. Epistylis (not contractile) and Carchesium (contractile) are true colonies with branching tree-like stalks.

Classification : Kingdom Protoctista, Phylum Ciliophora