  Estimates of the [O/H] metallicity of the star-forming gas in a sample of 66
CFRS galaxies between 0.47 < z < 0.92 have been made based on the flux ratios
of bright emission lines. Most galaxies (> 75%) have the [O/H] ~ 8.9
metallicities that are seen locally in galaxies of similar luminosities.
However, a minority (< 25%) appear to have significantly lower metallicities
[O/H] < 8.6 as indicated by high values of the Pagel R23 parameter. The high
metallicities of the majority of the galaxies suggest that they do not fade to
be low metallicity dwarf galaxies today. Only one of the 66 galaxies has an
optical emission line spectrum similar to the few Lyman break galaxies recently
observed at z ~ 3, emphasizing the differences with that population. The
inferred emission line gas [O/H] metallicity broadly correlates with luminosity
in both the rest B- and J-bands but with considerable scatter introduced. The
metallicity does not appear to correlate well with galaxy size, H-beta strength
or, with the very limited data available, the kinematics. The metallicity does
correlate well with the continuum optical-infrared colors in a way that could
be explained as a combination of effects, none of which should produce large
variations in the M/L ratio. These results support a "down-sizing" picture of
galaxy evolution rather than a "fading dwarf" picture in which the luminous
active galaxies at high redshift are highly brightened dwarf galaxies. The
overall change in metallicity of star-forming galaxies over the last half of
the age of the Universe appears to have been modest, Delta[O/H] = 0.08 +/-
0.06. This is consistent with the age-metallicity relation in the Galactic disk
and is broadly consistent with models for the chemical evolution of the
Universe, especially those that consider different environments.
