  A two-site spatial coagulation model is considered. Particles of masses $m$
and $n$ at the same site form a new particle of mass $m+n$ at rate $mn$.
Independently, particles jump to the other site at a constant rate. The limit
(for increasing particle numbers) of this model is expected to be
nondeterministic after the gelation time, namely, one or two giant particles
randomly jump between the two sites. Moreover, a new effect of induced gelation
is observed--the gelation happening at the site with the larger initial number
of monomers immediately induces gelation at the other site. Induced gelation is
shown to be of logarithmic order. The limiting behavior of the model is derived
rigorously up to the gelation time, while the expected post-gelation behavior
is illustrated by a numerical simulation.
