ABSTRACT
The most obvious of the larger social groups in Umor are the yepun. A kepun of Umor may be summarily and provisionally described as an exogamous patrilineal and territorial group, with rights to a delimited dwelling area in the village. Umor is no simple aggregation of perfectly formed yepun. The story of the prolonged debate that this involved reveals clearly the strength of the sentiment of kepun continuity, but the outcome demonstrated the possibility of fission. The Obeten Ogometu group, in which adoption has been responsible for present membership to a lesser extent presents an instance of the opposite tendency towards fission. While accretion tends to occur through the incorporation of individuals, fission follows more often from the separation of relatively large groups, and an early stage of the process appears to exist in this lineage.
