According to
Encyclopedia Britannica, the Volvox
genus contains about 20 different species (2015). These autotrophic green algae
live in fresh water where they form “spherical or oval hollow colonies” (2015).

These colonies can range from 500 to 60,000 cells joined together via cytoplasmic
filaments (2015). Their somatic cells each have two flagella and one chloroplast
(2015). These microorganisms engage in “phototaxis” by grouping the colony members
with larger “light reception” areas together to form an area specifically targeted
for photosynthesis (2015). Most Volvox
species reproduce asexually and sexually with some switching “primary modes of
reproduction” (2015).