In this paper, the results of redshift observations for Abell clusters with m10 less than 16.5 and medium-distant Zwicky clusters in a large region of the South Galactic Cap are presented. The region contains a possible filament of galaxies and galaxy clusters which includes the Perseus-Pisces Supercluster and has a total apparent length of over 300/h Mpc. The observed distribution of three-dimensional cluster alignments is compared with that for a random distribution of clusters constrained to have the same two-point spatial correlation function as the Abell clusters. The Kolmogorov-Smirnov test indicates less than 0.3 percent probability that the apparent filament could occur in the 'constrained random' samples. Some of the possible implications that the existence of such large structures might have for the more popular theories on the formation of galaxies and clusters are also discussed.