Evolution. In the article “The universal ancestor” by Carl R. Woese, which appeared in number 12, June 9, 1998, of Proc. Natl. Acad. Sci. USA (95, 6854–6859), the following correction should be noted. The second sentence of the fourth paragraph on page 6858 should read: “Given that metabolic genes tend to be laterally mobile and that the eukaryotes engage in lateral gene transfers, especially (but not exclusively) through endosymbioses, it is unreasonable to expect that the eukaryotes had no opportunity to sample the genes in question.”