  Recent surveys have allowed to derive the white dwarf mass distribution with
reasonable accuracy. This distribution shows a noticeable degree of structure
that it is often attributed to the evolution of close binaries in general, and
to mergers in particular. To analyze if the origin of this structure can be
attributed to the merger of double white dwarfs, we have used a simplified
population synthesis model that retains the essential processes of formation of
double degenerate binaries. Special care has been taken to avoid artifacts
introduced by discontinuities in the distribution functions. Our result is that
these structures are not probably due to mergers, but they can provide a deep
insight on the evolution of close binary systems.
