  Monte Carlo simulations of an atomistic solid-on-solid model are used to
study the effect of lattice misfit on the distribution of two-dimensional
islands sizes as a function of coverage $\Theta$ in the submonolayer
aggregation regime of epitaxial growth. Misfit promotes the detachment of atoms
from the perimeter of large pseudomorphic islands and thus favors their
dissolution into smaller islands that relieve strain more efficiently. The
number density of islands composed of $s$ atoms exhibits scaling in the form
\mbox{$N_s(\Theta) \sim \Theta / \langle s \rangle^2 \, g(s/\langle s
\rangle$)} where $\langle s \rangle$ is the average island size. Unlike the
case of homoepitaxy, a rate equation theory based on this observation leads to
qualitatively different behavior than observed in the simulations.
