First published in 1914, W. H. R. Rivers' hugely influential study was the first to effectively demonstrate the close connection between methods of denoting relationship or kinship and forms of social organisation, including those based on different forms of the institution of marriage. He also shows that the terminology of relationship has been rigorously determined by social conditions and that, therefore, systems of relationship furnish us with a most valuable instrument in studying the history of social institutions. This series of lectures was originally delivered by the author in May 1914, at the London School of Economics. They are based on the experiences of the Percy Sladen Trust Expedition to Melanesia in 1908.