Inspecti of photographs obtained with wide-angle telescopes sho' that the distribution of galaxies over the sky is distinctly nt miform. The observed dumpiness of the distribution of ga ies is believed to be due to a tendency for galaxies to occur in sters. A cluster of galaxies is usually regarded as a distinct >e of aggregate of matter. It is the purpose of this paper to investigate some aspects of the validity of the concept of a cluster of galaxies as a distinct type of organization intermediate between an individual galaxy and the universe as a whole. In other words, is a cluster of galaxies an indivisible unit or can it be divided into subclusters or even smaller units ? Alternatively one may inquire if clusters of galaxies are the largest aggregates of matter or if they are themselves constituents of still larger organizations. In attempting to answer these questions we find it instructive to consider first the "Local Group," which is presumably a rather typical example of a small cluster of galaxies. It is quite apparent that the members of this group are not distributed at random in space. The most striking example is the Andromeda Nebula with its two companions M 32 and NGC 205. A compact binary system is formed by the Magellanic Clouds. On a somewhat larger scale it is at once apparent that most of the members of the Local Group may be placed in two subgroups. One of these subgroups is formed by the Galaxy and the Magellanic Clouds. The other subgroup consists of NGC 147, NGC 185, NGC 205, M 31, M 32, M 33, and possibly NGC 404 and IC 10. The different orders of subclustering of the brightest Local Group members are shown schematically in Table I. It is well known that the surface distribution of galaxies in the region of the Virgo cluster is quite irregular. Some of this apparent irregularity may be due to a tendency toward subclustering within the Virgo cluster proper. More definite evidence of the existence of small-scale dumpiness in the Virgo cluster