Light micrograph of four Phacus sp. protists. Phacus belongs to the class Euglenophyceae and forms large, mostly flattened cells with a rigid shell. At the front end of the cell there is a swimming flagellum and usually a red eye spot. The cells have a large nucleus, many chloroplasts without pyrenoids and large paramylon grains as storage material, seen here as round, white structures. The focus plane is on the upper surface of the protist cells to show the striping of the cell surface. Microscopic contrast technique: Differential interference contrast. Magnification: 950x when printed 10 centimetres wide.