  In the canonical up-quark seesaw, the ratios of light neutrino masses are
more easily predicted than the masses themselves. Under explicitly enumerated
neccesary but minimal assumptions, these ratios are obtained, including
radiative corrections. The predictions remain uncertain only by the top quark
mass and triviality mass limit, and the power law of the seesaw. The tau
neutrino is specially affected by the non-linear effect of the heavy top quark
mass. The derived ratios have application to solar, atmospheric, and
cosmological neutrinos and laboratory neutrino oscillation searches. The seesaw
with charged lepton masses instead is briefly considered. Submitted to Phys
Lett B.
