The basic structure of the Nupe kinship system is the extended family: all individuals who can trace their descent to a certain initial, nucleus family-a husband and his wives-regard themselves as related and as forming one kindred. The effective kinship unit—the 'house' in the abstract sense of the word—expresses itself conspicuously in the recognition of a common family head, who is called, significantly, emitso, Owner of the House. Kinship membership itself and the access to the political and religious rights vested in it are determined by paternal descent. Political factors are also responsible for the development of the large units which characterize kinship among the ruling family. In Bida the situation is altered by a number of circumstances peculiar to the urban society. Space for local expansion being limited, families are much more widely scattered than in the village, even beyond the single efu, and the family section inhabiting one house is reduced to the smallest size.