All these findings indicate that the relative spatial density of galaxies of different luminosity depends on the location of the considered sample in the cluster. The fact that these type-dependent luminosity functions are invariant in shape from poor to rich environments, gives support to the hypothesis that they may be universal. The field of view is 40x30 arcmin. The evolutionary history of the morphological types should be no more indirectly inferred by the signatures that it leaves in the galaxy properties, but can be caught in the act. S0s in the intermediate redshift cluster for which we have morphological types of very high quality, and for which we can derive an E to S0 ratio with small error.
Distant clusters contain galaxies with disturbed morphologies and peculiar spectra.
The occurrence of these peculiarities varies from cluster to cluster and, on average, increases with redshift. In general, the change of galaxy properties is explained as the effect of some type of evolution.