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Whereas Volvox individuals have 500 to 60,000 cells arranged in a hollow sphere, some relatives, such as the Gonium species, have as few as four to 16 cells; others are completely unicellular.

The volvocine species Gonium pectorale — whose genome was just sequenced for the first time as part of the study — is right smack in the middle of that path, so much so it's pretty much in evolutionary purgatory between the two stages.

When Olson, who teaches evolutionary genomics at Kansas State University, removed the gene from a Gonium and put it in its unicellular relative, Chlamydomonas, the formerly single-celled organisms started clumping together to form colonies.

My mind swept back over evolution from star-dust to Kartabo compound, from Gonium to man, and to these leaf-cutting ants.

First a swimming lily, Stentor, a solitary animal bloom, twenty-five to the inch; Cothurnia, a double lily, and Gonium, with a quartet of cells clinging tremulously together, progressing unsteadily—materially toward the rim of my field of vision—in the evolution of earthly life toward sponges, peripatus, ants and man.