  We discuss the transitions of galaxy morphologies within the CDM paradigm
under the assumption of bulge formation in mergers and disk growth via cooling
of gas and subsequent star formation. Based on the relative importance of these
two competing processes it is possible to make predictions on the expected
morphological mix of galaxies. In particular we here discuss the generation of
massive disk galaxies with low bulge-to-total mass ratios. Our results indicate
that it is difficult to generate enough massive disk galaxies with B/T $< 0.2$
via major mergers and subsequent disk re-growth, if during the major merger
progenitor disks get disrupted completely. On average low B/T galaxies must
have had there last major merger at $z \ge 2$. The main limiting factor is the
ability to re-grow massive disks at late times after the last major merger of a
galaxy. Taking into account the contribution from minor mergers ($4 \ge
M_1/M_2$, $M_1 \ge M_2$) to the formation of bulges, we recover the right
fraction of massive low B/T disk galaxies, indicating that minor mergers play
an important role in the formation of massive low B/T disk galaxies.
