Volvox aureus is a chlorophyte or green alga. Many species of chlorophytes are flagellate and motile, other are immobile but often have a flagellate stage at some time in their life cycle. Volvox forms a spherical colony. All the small cells of the colony possess two flagella and a small eyespot. With this the colony is able to swim towards the light. Zoom in to see more details.
Find out much more about it in the Micscape article Volvox, one of the seven wonders of the microworld.