The aggregation of adatoms into 2D islands is studied as a function of coverage FTHETA and the ratio of surface diffusion rate to deposition rate gerR=D/F by Monte Carlo simulations of a model of epitaxial growth that permits atoms to detach from island edges at a rate determined by a pair bond energy ${\mathit{E}}_{\mathit{N}}$. The total island density is observed to saturate before coalescence becomes important. In this regime, the density of adatoms ${\mathit{N}}_{1}$\ensuremath{\sim}${\mathit{FTHETA}}^{\mathrm{\ensuremath{-}}\mathit{r}}$${\mathit{gerR}}^{\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\omega}}}$ while the density of islands composed of sg1 atoms ${\mathit{N}}_{\mathit{s}}$\ensuremath{\sim}FTHETA〈s${\mathrm{〉}}^{\mathrm{\ensuremath{-}}2}$g(s/〈s〉) where the average island size 〈s〉\ensuremath{\sim}${\mathit{FTHETAgerR}}^{\mathit{x}}$. The exponents r, \ensuremath{\omega}, and \ensuremath{\chi} vary smoothly with ${\mathit{E}}_{\mathit{N}}$.