Figure 6: (a) Number of particles which diffused a distance 
in 
msec from a sample of 15000 trajectory steps.
The thin line is a fit to eqn. (16).
(b) The evolution in time of the square of the width, 
,
from fits such as that in (a).
The linear least-squares fit to eqn. (17) provides
a measurement of the spheres' long-time self-diffusion coefficient.
The unresolvable offset 
in this fit is consistent with
our estimated measurement error for particle locations for
a dilute suspension with minimal caging.