I find Bothrostoma undulans rarely but regularly in the Purren pond and the Simmelried, especially in decaying leaves. The ciliate is very conspicuous by its large, broad adoral zone (s. figs. 1 b and 2 a-c). This runs from left to right diagonally across the ventral side of the cell body and turns to the left just before the mouth opening (s. fig. 2 b). More difficult to recognize is the paroral membrane, which lies like a triangular sail over the adoral zone. The paroral membrane originates on the right side of the adoral zone and runs in parallel to it (s. fig. 2 c). Its complete shape is not easily seen, but the long cilia of the membrane lie like a curtain over the adoral zone in lateral view (s. figs. 1 a and 1 d). The macronucleus was also kidney-shaped in some specimens in my population (s. fig. 3) and enclosed partly the micronucleus. The length and numbers of caudal cilia also appear to be quite variable. I could also observe specimens with much longer caudal cilia than in the specimens shown below. The pellicle is clearly granulated by mucocysts, which are arranged in parallel stripes (s. fig. 4 b). In the cytoplasm I could detect symbiotic bacteria in all specimens, but I did not examine them more closely.