MODE OF CONJUGATION IN HOMOTHALLIC CELLS OF SCHIZOSACCHAROMYCES POMBE

When homothallic cells of Schizosaccharomyces pombe were plated on agar sporulation medium, a few residual divisions were usually observed before induction of conjugation and sporulation. Four cells resulting from the last two residual divisions were usually lined; the "four-lined-cell" formed. Each four-lined-cell contained only one zygote by sistercell-or non-sistercell-copulation, and never two zygotes by two sistercell-copulations. Some of the remaining non-zygotic sistercells divided once again and resulted in the new formation of the four-lined-cell which contained only one zygote. The remaining non-zygotic cell of the four-lined-cell could conjugate with that of another four-lined-cell. These results suggest that the four-lined-cell is to be regarded as one unit with respect to zygote formation.