Since the last International Astronomical Union Symposium that dealt with matters cosmological, there have been dramatic advances, both on the observational and theoretical fronts. Modern high-efficiency detectors have made possible extensive magnitude-limited redshift surveys, which have permitted observational cosmologists to construct three-dimensional maps of large regions of space. What seems to emerge is a distribution of matter in extensive, flat, but probably filamentary, and possibly interconnected, superclusters, serving as interstices between vast voids in space. Meanwhile,...