"spinning" flagellates. Unicellular photosynthetic organisms with chlorophylls a and c. Food is stored as starch. Cell walls contain cellulose. Most of the organisms in this divisions have two lateral flagella, one of which beats in a groove that encircles the organism. They probably have no form of sexual reproduction, and their mitosis is unique. Nearly 2,000 living species in the Division Dinoflagellata.