Differential interference contrast (DIC) light micrograph of the freshwater alga Volvox aureus. Volvox forms large (up to 2 millimetres), spherical colonies with up to several thousand two-flagellated single cells arranged in a regular pattern in the periphery of a colourless jelly. The focus in this picture is above the surface of a colony onto the fine tunnels in which the two flagella of each cell are led out through the thick outer colony wall. Magnification: x670 at a print width of 10 centimetres.