Volvox
in botany, the typical genus of Volvocineæ, with one species, V. globator. To the naked eye it resembles a minute pale green globule floating about in the water. Under the microscope it is seen to be a spherical membranous sac, studded with innumerable green points, really apertures giving exit to cilia, which enable it to roll over and over in the water. Within the sac are various dense globules, generally green in summer, but often of an orange color in autumn and early winter. They are zoöspore-like bodies, each sending a pair of cilia through separate orifices. There is a reddish brown spot and a contractile vacuole. They are found abundantly in clear pools on open commons and similar localities.