  We discuss a new method for inferring the stellar mass of a distant galaxy of
known redshift based on the combination of a near-infrared luminosity and
multi-band optical photometry. The typical uncertainty for field galaxies with
I<22 in the redshift range 0<z<1 is a factor 2. We apply this method to a
newly-constructed sample of 321 field galaxies with redshifts and Hubble Space
Telescope morphologies enabling us to construct the stellar mass density
associated with various morphologies as a function of redshift. We find a
marked decline with time in the stellar mass associated with peculiar galaxies
accompanied by a modest rise in that observed for ellipticals. The result
suggests that peculiars decline in abundance because they transform and merge
into regular systems. The star formation rate per unit stellar mass indicates
that massive systems completed the bulk of their star formation before redshift
one, whereas dwarfs continue to undergo major episodes of activity until the
present epoch.
