  Considering perturbation growth in spherical Top-Hat model of structure
formation in a generalized Chaplygin gas dominated universe, we want to study
this scenario with a modified Chaplygin gas model. The evolution of background
and collapsed region parameters are found for different cases. The stability of
the model and the collapse time rate are considered in different cases. The
turn-around redshifts are also computed; the results are in relatively good
agreement with current observational data.
