  Computer simulations were used to study the gel transition occurring in
colloidal systems with short range attractions. A colloid-polymer mixture was
modelled and the results were compared with mode coupling theory expectations
and with the results for other systems (hard spheres and Lennard Jones). The
self-intermediate scattering function and the mean squared displacement were
used as the main dynamical quantities. Two different colloid packing fractions
have been studied. For the lower packing fraction, $\alpha$-scaling holds and
the wave-vector analysis of the correlation function shows that gelation is a
regular non-ergodicity transition within MCT. The leading mechanism for this
novel non-ergodicity transition is identified as bond formation caused by the
short range attraction. The time scale and diffusion coefficient also show
qualitatively the expected behaviour, although different exponents are found
for the power-law divergences of these two quantities. The non-Gaussian
parameter was also studied and very large correction to Gaussian behaviour
found. The system with higher colloid packing fraction shows indications of a
nearby high-order singularity, causing $\alpha$-scaling to fail, but the
general expectations for non-ergodicity transitions still hold.
