Motivated by the null-detection of isolated, extra-galactic clouds of
neutral hydrogen, \HI , without a stellar component, the goal of this
project is to determine to what extent it is possible for star formation
to be supressed through heating and the photodestruction of \htwo\ by the
action of the cosmic background radiation (CBR) alone. This requires two
things: a model for the distribution and composition of the gas cloud, and
some criterion for star formation.  Assuming that the process of galaxy
formation is self-similar over many decades in mass, I apply the
analytical model of Mo, Mao & White (1998) to determine the distribution
of mass for gas clouds in the mass range $10^{6}$ M\sun\ -- 10$^{10}$
M\sun.  I also extend an established formalism for determining the height
dependence of the disk volume density, incorporating a complete treatment
of the effects of rotation and the dark halo.  Finally, I determine the
relative abundances of nine chemical species in the presence of the
photodestructive CBR, to determine the level of cooling and potential star
formation.  I find that at least 50 percent of all putative `galaxies
without stars' with baryonic masses in the range given are expected to be
unstable to star formation.  This result gives a strong argument that high
velocity clouds --- \HI\ clouds devoid of stars and at undetermined
distances --- are satelites of the Milky Way, rather than sub-galactic
members of the Local Group.