Wild type phenotypes of three volvocine species. (A) Chlamydomonas reinhardtii (strain 137c), a unicellular relative of Gonium. (B) Volvox carteri f. nagariensis (female strain Eve), a spheroidal multicellular relative of Gonium, which consists of ~2000 small, terminally differentiated, somatic cells at the surface and ~16 reproductive cells in the interior. (C) A rhomboidal, flat colony of Gonium pectorale (strain SAG 12.85) with 16 cells prior to the onset of cleavage. (D) A G. pectorale (strain SAG 12.85) colony in the stage of embryogenesis. Each of the 16 cells forms a 16-cell plakea in 4 longitudinal cell cleavages.