Volvox is a genus of multicellular freshwater free-swimming green algae. It is largely used for developmental biology, and to study the transition from single celled to multicellular forms of life. The larger spheres are colonies of small biflagellate cells with smaller aflagellate round colonies inside which are the daughter colonies, or the baby algae. Specialized biflagellated cells are responsible for locomotion and spinning movements toward a light source so they can produce sugar by photosynthesis. Those biflagellated cells also possess an eyespot which is responsible for detecting light and guide the colony towards optimal light conditions. These flagellated cells that compose the large mother colony are all interconnected by small cytoplasmic bridges to allow nutrient transfer and communication between cells.