  The warm ionized gas in low-mass, metal-poor starforming galaxies is
chemically homogeneous despite the prevalence of large H II regions which
contain hundreds of evolved massive stars, supernovae, and Wolf-Rayet stars
with chemically-enriched winds. Galaxies with large Wolf-Rayet star content are
chemically indistinguishable from other vigorously star-forming galaxies.
Furthermore, no significant localized chemical fluctuations are present in the
vicinity of young star clusters, despite large expected chemical yields of
massive stars. An ad-hoc fine-tuning of the release, dispersal and mixing of
the massive star ejecta could give rise to the observed homogeneity, but a more
probable explanation is that fresh ejecta from massive stars reside in a
hard-to-observe hot or cold phase. In any case, the observed chemical
homogeneity indicates that heavy elements which have already mixed with the
warm interstellar medium (thus accessible to optical spectroscopy) are
homogeneously dispersed over scales exceeding 1 kpc. Mixing of fresh ejecta
with the surrounding warm ISM apparently requires longer than the lifetimes of
typical H II regions (>10^7 yrs). The lack of observed localized chemical
enrichments is consistent with a scenario whereby freshly-synthesized metals
from massive stars are expelled into the halos of galaxies in a hot, 10^6 K
phase by supernova-driven winds before they cool and ``rain'' back down upon
the galaxy, creating gradual enrichments on spatial scales >1 kpc.
