I find Stentor coeruleus frequently and regularly, especially in the Simmelried and Ulmisried. The specimens are easy to recognize due to their size and striking blue-green colouring. In fresh samples, the specimens usually swim around in a contracted form. In a micro-aquarium with a high layer thickness, however, they quickly begin to attach themselves to detritus particles and stretch out. Stentor coeruleus shows an amazing ability to stretch. When fully elongated, most of the body is almost tapered like a thread, except for the trumpet-shaped “head” (s. figs. 1 and 2). The elongated body bends back and forth as food is swirled towards it. Single-celled algae, dinoflagellates and bacteria serve as food.

The macronucleus is moniliform and consists of 10-20 spherical nodules (s. figs. 3 a and 5). This makes it easy to distinguish Stentor coeruleus from Stentor multiformis, which is also blue-green in color. The micronuclei of Stentor coeruleus are attached to the moniliform macronucleus, but also in the adjacent cytoplasm (s. fig. 6). According to my observations, the micronuclei are elliptical in shape and about 5–6 µm long (s. fig. 6).