I find Trachelomonas volvocina frequently and regularly in the Simmelried between floating plant masses. The species is easy to recognize by its spherical, smooth lorica. In my population, the lorica aperture is usually thickened in a ring shape (s. fig. 1 a-d). However, there are also forms without such a thickening. Trachelomonas volvocina is said to have two chloroplasts, each with a pyrenoid. But since the specimens in my population were all completely filled with paramylon grains, I could not recognize this exactly (s. fig. 1 c). The eyespot of Trachelomonas volvocina is very large and conspicuous (s. fig. 1 a).

The similiar species Trachelomonas cervicula has an apical pore surrounded by a low flat thickening and with a cylindrical canal extending inwards into the lorica. The lorica of the second similar species, Trachelomonas curta, is compressed and appears oval in apical view.