  The formation and evolution of disk galaxies in the cosmological context is
studied. We consider the observable properties of disk galaxies and treat the
disk formation and galactic evolutionary processes in a self-consistent
fashion. We find the matter accretion regime to be the dominant ingredient in
establishing the Hubble sequence. The accretion regime is a phenomenon directly
related to the statistical properties of the primordial density fluctuations
from which disk galaxies emerged. In this paper we assumed a Gaussian density
field and a standard CDM model.
