88 AFRICAN POLITICAL SYSTEMS
duties for each other, but this form of social grouping does not seem to affect the political organization at all at the present day.1
Within the clan, smaller lineage groups are recognized. These have no distinct name; though the Bemba often refer to them as 'houses' (amaianda, sing, irjandd) of the same clan. Such a house consists of the direct descendants of one particular ancestress traced back to three or four generations—five at the most. Within this smaller descent group, succession to office is usually limited, and chieftainships tend to become hereditary within three or four generations in such lines.2 Social replacement of one man for another, either as an heir, an official in a religious ceremony, in fulfilment of a marriage contract (in the case of a woman), or in compensation for blood guilt in the old days, tends and tended to take place within the 'house5 and not the clan, though members of the umukoa do replace each other if there is no one more nearly related within the irjanda to do so.
It is the smaller descent-group which is important in considering the influence of the ancestral spirits (imipashi, sing, umupashf) over the living, either as affecting the welfare of their descendants in general or as entering the wombs of pregnant women of that descent-group to act as guardian spirits to the children as yet unborn.
Apart from the descent-group that determines his status, there is the body of kinsmen with whom a Bemba co-operates actively in daily life. These are the people with whom he may choose to live, and who gather together at any important event in his life, such as . marriage, the birth of a child, illness, or a death. This group is known by a distinct term, the ulupwa* It has a bilateral basis, since it is composed of the near relatives on both sides of the family and also relatives in law. The balance between the powers of the maternal and paternal relatives is a very even one in Bemba society, in spite of the legal emphasis on the matrilineal side, and the ties uniting the members of the ulupwa are very strong.3 Though it is
1 cf. my 'Reciprocal Clan Relationships among the Bemba of North-Eastern Rhodesia*, Man, December, 1937.
2 The late Nkula, Bwalya Cangala, claimed, in the course of a succession dispute, that his near relatives, the children of his grandmother, Nakasafye, must now be considered as a separate 'house', as distinct from the children and grandchildren of her sister, Mukukamfumu II (cf. chart on p. 102).
3 cf. my 'Mother-right in Central Africa' in Essays presented to C. G. Selizman (1934).