Stentor amethytinus is by far the most common species of the genus Stentor in the Simmelried area where I found it. In the sample beakers they form sometimes black coatings on the side facing the light. Stentor amethystinus is particularly common in the summer months.

At low magnifications, the specimens usually appear black, as they are opaque due to the symbiotic algae and the purple granules. The specimens rarely settle under the cover glass. Extended specimens are funnel-shaped with a short stalk (s. fig. 1 a-b). This distinguishes them from other Stentor species, which are usually slenderly elongated and trumpet-shaped. Another characteristic feature is the purple-colored granula, which is arranged in rows in the pellicle (s. figs. 2 and 3). The specimens are usually very strongly purple in color. The colored granules are also partially distributed in the cytoplasm. Symbiotic algae are densely arranged below the pellicle. The algae all have their own nucleus, but do not appear to be of the Chlorella type, as they do not have a pyrenoid (s. fig. 7). The spherical macronucleus is surrounded by many micronuclei. There should be more than 20. In my population there were usually fewer, but more than 10. Each micronucleus is surrounded by a layer of purple granules, which makes them easily recognizable (s. figs. 5 and 6).