  The formation of low surface brightness galaxies is an unavoidable prediction
of any hierarchical clustering scenario. In these models, low surface
brightness galaxies form at late times from small initial overdensities, and
make up most of the faint end of the galaxy luminosity function. Because there
are tremendous observational biases against finding low surface brightness
galaxies, the observed faint end of the galaxy luminosity function may easily
fall short of predictions, if hierarchical structure formation is correct. We
calculate the number density and mass density in collapsed objects as a
function of baryonic surface density and redshift, and show that the mass in
recently formed low surface brightness galaxies can be comparable to the mass
bound into ``normal'' high surface brightness galaxies. Because of their low
gas surface densities, these galaxies are easily ionized by the UV background
and are not expected to appear in HI surveys. Low surface brightness galaxies
(LSBs) are not a special case of galaxy formation and are perhaps better viewed
as a continuance of the Hubble sequence.
