  We give the explicit equations for a P^3 x P^3 embedding of the Jacobian of a
curve of genus 2, which gives a natural analog for abelian surfaces of the
Edwards curve model of elliptic curves. This gives a much more succinct
description of the Jacobian variety than the standard version in P^{15}. We
also give a condition under which, as for the Edwards curve, the abelian
surfaces have a universal group law.
