  We study the late time flow structure of Richtmyer-Meshkov instability.
Recent numerical work has suggested a self-similar collapse of the development
of this instability at late times, independent of the initial surface profile.
Using the form of collapse suggested, we derive an analytic expression for the
mass-velocity relation in the spikes, and a global theory for the late time
flow structure. We compare these results with fluid dynamical simulation.
