The central thesis of this book is that Volvox and its unicellular and colonial relatives provide a wholly unrivaled opportunity to explore the proximate and ultimate causes underlying the evolution from unicellular ancestors of multicellular organisms with fully differentiated cell types. A major portion of the book is devoted to reviewing what is known about the genetic, cellular and molecular basis of development in the most extensively studied species of Volvox: V. cateri, which exhibits a complete division of labor between mortal somatic cells and immortal germ cells. However, this topic...