  Recently, we have presented the first large-scale radiative transfer
simulations of reionization. Here we present new simulations which extend the
source halo mass range downward to 10^8M_solar, to capture the full range of
halo masses thought to be primarily responsible for reionization by their star
formation following atomic hydrogen radiative cooling and gravitational
collapse. Haloes below about 10^9M_solar, however, are subject to Jeans-mass
filtering in the ionized regions, which suppresses their baryonic content and
their ability to release ionizing radiation. By including these smaller-mass
haloes but accounting for their suppression, too, we find that reionization is
``self-regulating,'' as follows. As the mean ionized fraction rises, so does
the fraction of the volume within which suppression occurs. Hence, the degree
of suppression is related to the mean ionized fraction. Since low-mass haloes
with high emissivity achieve a given mean ionized fraction earlier than do
those with low efficiency, Jeans-mass filtering compensates for the difference
in the emissivity of the suppressible haloes in these two cases. As a result,
in the presence of lower-mass source haloes, reionization begins earlier, but
the later stages of reionization and the time of overlap are dictated by the
efficiency of the higher-mass haloes, independent of the efficiency of the
suppressible, lower-mass haloes. Reionization histories consistent with current
observational constraints are shown to be achievable with standard stellar
sources in haloes above 10^8M_solar. Neither minihalos nor exotic sources are
required, and the phenomenon of ``double reionization'' previously suggested
does not occur. (abridged)
