today Bernhard, my family and I were searching for some interesting water-samples in the area of an old railway tunnel, which is unused for several years now. My yield was only poor, with the exception of this Meridion:
40x/0,75 PlanNeofluar objective, oblique illumination
Meridion is characterized by its fan-shaped colonies which make this genus unmistakable. Furthermore there exists only one species, Meridion circulare. So, this one makes life easy for the microscopist.
Enjoy!
