Fig. 1.

Volvocine green algae arranged according to typical colony radius R. The lineage ranges from the single-cell Chlamydomonas reinhardtii (A), to undifferentiated Gonium pectorale (B), Eudorina elegans (C), to the soma-differentiated Pleodorina californica (D), to the germ–soma differentiated V. carteri (E), V. aureus (F), and even larger (e.g., V. gigas with a radius of 1 mm). In species in which two cell types can be identified, the smaller are somatic cells and the larger are reproductive cells. Note that the number of cells in Volvox species ranges from 1,000 (e.g., V. carteri) to 50,000 (e.g., V. barberi).