  We investigate the formation of clusters of galaxies in an expanding universe
using a new code that regrids at a region of high density. In particular we
investigate two models for the initial conditions, both with the standard CDM
power spectrum - one has $\Omega = 1$ and the other $\Omega = 0.2$. Both
universes have $H_0 = 100 \kms\mpc^{-1}$ and $\Lambda = 0$. The level of
substructure in the final cluster can be used as a discriminant of the cosmic
density. We discuss various statistics which can be measured observationally
from clusters of galaxies, that can be used to discriminate between the two
models. We find that most of the statistics that use the clusters' member
galaxies may not be the best measures of substructure. Statistics that rely
more on X-ray maps and other observables depending more directly on the mass
distribution could be better discriminants of $\Omega$.
