  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 can be useful in constructing
theoretical models for the bimaximal pattern. We illustrate this by a simple
example.
