  We discuss how luminosity and space distribution of galaxies are naturally
linked in view of their multifractal properties. In particular we show that the
mass (luminosity) function corresponding to a multifractal distribution in a
given observed volume, consists of a power law followed by an exponential
cut-off. This implies that the amplitude $\phi^*$ of the Schechter function
scales with the sample depth, as confirmed by various observational data. This
effect is analogous to the scaling of the space density due to the fractal
nature of the space distribution. This has the important consequence that the
luminosity function can be properly defined only in a volume limited sample.
Also the so-called "luminosity segregation" and the concept of bias correspond
to a natural consequence of multifractality. This implies however that they
should be considered from a different perspective with respect to the usual
one. Such a concept allows us to unify the space and luminosity distributions
as being shaped by a single cause:multifractality which should therefore claim
a central stage in theoretical investigations.
