Volvox is one of the best-known chlorophytes and is the most developed in a series of genera that form spherical colonies. Each Volvox is composed of numerous flagellate cells similar to Chlamydomonas, on the order of 1000–3000 in total, interconnected and arranged in a glycoprotein-filled sphere (coenobium). The cells swim in a coordinated fashion, with a distinct anterior and posterior – or since Volvox resembles a little planet, a 'north' pole and a 'south' pole. The cells have eyespots, more developed near the anterior, which enable the colony to swim towards light.
An asexual colony includes both somatic, or vegetative, cells, which do not reproduce, and gonidia near the posterior, which produces new colonies through repeated division. These daughter colonies are initially held within the parent and have their flagella directed inwards. Later, the parent disintegrates and the daughters invert. In sexual reproduction two types of gametes are produced. Volvox species can be monoecious or dioecious. Male colonies release numerous microgametes, or sperm, while in female colonies single cells enlarge to become oogametes, or eggs.
According to Chamberlain (1932),
The individual algae are connected by thin strands of cytoplasm, called protoplasmates.