Paramecium caudatum and the predominant zooplanton organisms were registered in the studied pond of the Botanical Garden of the Jagiellonian University in Krakow. The finding of Stentor coeruleus indicates an improvement in the environmental conditions in Krakow, connected with the partial liquidation of the huge steelworks.
E. Przybos, Department of Experimental Zoology, Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Slawkowska 17, 31-016 Krakow, Poland