Volvox

Volvox, a genus of simple organisms which some authorities regard as animals and others as plants, but which are in fact not very emphatically the one or the other. They consist of green flagellate cells, united by protoplasmic bridges in a hollow spherical colony, and occur in ponds, canals, and clear fresh-water pools. Botanists claim them as Algae, referring them to a family of the order Coccophyceæ; zoologists claim them as animals, as colonial flagellate Infusorians. Each unit of the colony is somewhat like the common Hæmatococcus; and sometimes there may be as many as 12,000 forming one ball, which then measures about 1 mm. in diameter. Volvox is a very beautiful organism, and is full of interest to the biologist. Thus, as regards reproduction, one may be found quite asexual in its multiplication, another may be described as parthenogenetic, a third produces special male and female cells, while in others the sexes are separate. Within one species all these phases may occur, epitomising the whole evolution of sex. As a very simple many-celled organism Volvox also gives some hint as to transition from Protozoa to Metazoa. Nearly related are the genera Eudorina, Pandorina, Gonium, and Stephanosphaera.