Bimaximal Neutrino Mixing and Neutrino Mass Matrix

We show that the bimaximal neutrino mixing pattern suggested by the solar and atmospheric neutrino data can be derived from the maximal, symmetric , four neutrino mixing in the limit that one of the neutrinos is made heavy. Imposing the constraints of no neutrinoless double beta decay and a 20% hot dark matter component of the universe leads to a three neutrino mass matrix recently suggested by Georgi and Glashow. Our result will be of interest in constructing theoretical models for the bimaximal pattern.