  Quantitative measures of central light concentration and star formation
activity are derived from R and Halpha surface photometry of 84 bright S0-Scd
Virgo Cluster and isolated spiral galaxies. For isolated spirals, there is a
good correlation between these two parameters and assigned Hubble types. In the
Virgo Cluster, the correlation between central light concentration and star
formation activity is significantly weaker. Virgo Cluster spirals have
systematically reduced global star formation with respect to isolated spirals,
with severe reduction in the outer disk, but normal or enhanced activity in the
inner disk. Assigned Hubble types are thus inadequate to describe the range in
morphologies of bright Virgo Cluster spirals. In particular, spirals with
reduced global star formation activity are often assigned misleading early-type
classifications, irrespective of their central light concentrations. 45+-25% of
the galaxies classified as Sa in the Virgo Cluster sample have central light
concentrations more characteristic of isolated Sb-Sc galaxies. The misleading
classification of low concentration galaxies with low star formation rates as
early-type spirals may account for part of the excess of `early-type' spiral
galaxies in clusters. Thus the morphology-density relationship is not all due
to a systematic increase in the bulge-to-disk ratio with environmental density.
