Phase contrast photomicrograph of Paramecium bursaria. A living specimen of this ciliate protozoan was trapped under a cover glass and slightly compressed by carefully removing water from the edge of the cover with a strip of filter paper. Note the hair-like cilia with which it swims, and also the green symbiotic cells of Zoöchlorella. Careful observation of the photomicrograph reveals a macronucleus with micronucleus in a notch, the protozoan's gullet (grey line in front of the micronucleus), and two contractile vacuoles with radiating feeder canals. The objective was a 40x/0.65 NA achromat with a Reichert Zetopan microscope. The camera system was a Reichert Zetopan with an Exacta camera body. A Zeiss microflash illumination was utilized to make the 0.5 micro second exposure. The film was Kodachrome 25. (125x)