The old theories of tribal dichotomy, the discussions about the' origins' of ' phratries ' or ' moieties' and
25 of the duality in tribal subdivisions, never entered into the inner or differential foundations of the external phenomenon of halving. The recent treatment of the , dual organization' by the late Dr. Rivers and his school suffers badly from the defect of looking for recondite causes instead of analysing the phenomenon itself. The dual principle is neither the result of , fusion' nor ' splitting' nor of any other sociological cataclysm. It is the integral result of the inner symmetry of all social transactions, of the reciprocity of services, without which no primitive community could exist. A dual organization may appear clearly in the division of a tribe into two 'moieties' or be almost completely obliterated-but I venture to foretell that wherever careful inquiry be made, symmetry of structure will be found in every savage society, as the indispensable basis of reciprocal obligations.