Correction

EVOLUTION. For the article “The origin of the eukaryotic cell: A genomic investigation,” by Hyman Hartman and Alexei Fedorov, which appeared in number 3, February 5, 2002, of Proc. Natl. Acad. Sci. USA (99, 1420–1425; First Published January 22, 2002; 10.1073/pnas.032658599), the authors note that, on page 1421, the following sentence should be added at the end of the first paragraph of the Materials and Methods, and the reference below should be added to the reference list. “The Giardia database used in this paper is available at www.mbl.edu/Giardia. This database is described by McArthur et al. (24).” 1.  McArthur, A. G., Morrison, H. G., Nixon, J. E., Passamaneck, N. Q., Kim, U., Hinkle, G., Crocker, M. K., Holder, M. E., Farr, R., Reich, C. I., et al. (2000) FEMS Microbiol. Lett. 189, 271–273.