  Relying on samples of disk galaxies for which a detailed photometric
bulge/disk decomposition has been provided in the literature, we examine the
dependence of the bulge-to-disk luminosity ratio (B/D) on the blue absolute
luminosity and on the environmental density. In our statistical analysis of
various B/D data sets we pay particular attention to disentangling the role
played by the galaxy morphology--galaxy density relation. Besides, we focus our
attention on nearby ($z<0.01$) galaxies, for which we can provide a
three-dimensional characterization of the local galaxy density. We find that
the observed tendency of galaxies to have greater B/D with increasing galaxy
density simply reflects the average decline of B/D towards later morphological
types together with the morphology--density relation. This relation tends to
give rise also to a greater proportion of bright bulges in denser regions,
because the decrease of B/D towards later types is mostly due to a dimming of
the bulge rather than to a brightening of the disk. But when we remove the
effect induced by the morphology--density relation, we detect no clear evidence
of a dependence of B/D on galaxy density. Furthermore, B/D turns out to be
substantially unrelated to the blue absolute magnitude of the galaxy. We
briefly discuss to what extent our results (partially) disagree with previous
claims.
