  A previous short analysis of the seesaw mechanism, based on quark-lepton
symmetry, experimental data and hierarchical neutrino spectrum, is enlarged to
include small but not zero U_{e3}, inverted mass hierarchy, and the qualitative
effect of Majorana phases. The structure of the heavy neutrino mass matrix
obtained in several cases is discussed. We find two leading forms for this
matrix. One is diagonal and stands at the unification scale or above. The other
is off-diagonal and stands at the intermediate scale.
