  Galaxy morphological and spectroscopic types should be nearly independent of
apparent magnitude in a local, magnitude-limited sample. Recent luminosity
function surveys based on morphological classification of galaxies are
substantially more successful at passing this test than surveys based on
spectroscopic classifications. Among spectroscopic classifiers, those defined
by small aperture fibers (ESP, LCRS) show far stronger systematic
classification biases than those defined by large apertures (APM). This effect
can be easily explained as an aperture bias, whereby galaxies with globally
late-type spectra are assigned earlier spectral types which depend on the
redshift and luminosity of the galaxy. The effect is demonstrated by extracting
successively larger aperture spectra from long-slit spectroscopy of nearby
galaxies. This systematic classification bias is generic, and the 2dFGRS and
SDSS surveys will show similar systematic biases in their spectral types. We
suggest several methods for correcting the problem or avoiding it altogether.
If not corrected, this aperture bias can mimic galaxy evolutionary effects and
distort estimates of the luminosity function.
