  I develop a high velocity galaxy collision model to explain a rare but
puzzling phenomenon, namely the apparent existence of ultra-diffuse galaxies
with little dark matter. Predictions include simultaneous triggering of
overpressured dense clouds to form luminous old globular clusters, a protogroup
environment to generate high relative velocities of the initially gas-rich
galaxies in the early universe, and spatially separated dark halos, possibly
detectable via gravitational lensing and containing relic low metallicity stars
with enhanced [alpha/Fe] at ultralow surface brightness.
