  Hubble Space Telescope images of high-redshift galaxies selected via color
and photometric redshifts are used to examine the size and axial-ratio
distribution of galaxies as a function of redshift at lookback times t > 8 Gyr.
These parameters are measured at rest-frame UV wavelengths (1200-2000
Angstroms) on images with a rest-frame resolution of less than 0.8 kpc. Galaxy
radii are found to scale with redshift approximately as the inverse of the
Hubble parameter H(z). This is in accord with the theoretical expectation that
the typical sizes of the luminous parts of galaxies should track the expected
evolution in the virial radius of dark-matter halos. The mean ratio of
semi-major to semi-minor axis for a bright well-resolved sample of galaxies at
z ~ 4 is b/a = 0.65, suggesting that these Lyman break galaxies are not drawn
from a spheroidal population. However the median concentration index of this
sample is C = 3.5, which is closer to the typical concentration indices, C ~ 4,
of nearby elliptical galaxies than to the values, C<2 for local disk galaxies
of type Sb and later.
