  The impact of a drop onto a liquid layer and the subsequent splash has
important implications for diverse physical processes such as air-sea gas
transfer, cooling, and combustion. In the {\it crown splash} parameter regime,
the splash pattern is highly regular. We focus on this case as a model for the
mechanism that leads to secondary droplets, and thus explain the drop size
distribution resulting from the splash. We show that the mean number of
secondary droplets is determined by the most unstable wavelength of the
Rayleigh-Plateau instability. Variations from this mean are governed by the
width of the spectrum. Our results for the crown splash will provide the basis
for understanding more complicated splashes.
