VOLVOX, a well-known genus of organisms claimed by zoologists to belong to the Protozoa (q.v.), but perhaps more justi fiably placed by botanists in the Chlorophyceae, a section of the Algae (q.v.). Vo/vox consists of spherical colonies of cells, all in protoplasmic connection with their neighbours and each bearing a pair of cilia. These beat in regular co-ordination, imparting a
rolling motion to the colony. New colonies are formed from special cells set apart for this purpose and grow within the central cavity of the mother-colony. Sexual reproduction also occurs. (See ALGAE ; PROTOZOA.)