Florida is not only near Guadalcanar where the cross-cousin marriage is practised, (the two islands are within sight of one another), but their cultures are very closely related. In such a case the probability that the single feature of the Florida system which follows from the cross-cousin marriage has actually had that form of marriage as its antecedent becomes very great, and this conclusion becomes still more probable when we find that in a third island, Ysabel, closely allied in culture both to Florida and Guadalcanar, there is a clear tradition of the former practice of the cross-cousin marriage although it is now only an occasional event. Again, in one district of San Cristoval in the Solomons the term _fongo_ is used both for the father-in-law and the father’s sister’s husband, and _kafongo_ similarly denotes both the mother-in-law and the mother’s brother’s wife. This island differs more widely from Guadalcanar in culture than Florida or Ysabel, but the evidence for the former existence of the marriage in these islands gives us more confidence in ascribing the common designations of San Cristoval to the cross-cousin marriage than would have been the case if these common designations had been the only examples of such possible survivals in the Solomons. Speaking in more general terms, one may say that the probability that the common nomenclature for two relatives is the survival of a form of marriage becomes the greater, the more similar is the general culture in which the supposed survival is found to that of a people who practise this form of marriage. The case will be greatly strengthened if there should be intermediate links between the supposed survival and the still living institution. When we find a feature such as that of the Florida system among a people none of whose allies in culture practise the cross-cousin marriage, the matter must be far more doubtful. In the present state of our knowledge we are only justified in making such a feature the basis of a working hypothesis to stimulate research and encourage us to look for other evidence in the neighbourhood of the place where the feature has been found. Our knowledge of the social institutions of the world is not yet so complete that we can afford to neglect any clue which may guide our steps. I propose briefly to consider two regions, South India and North America, to show how they differ from this point of view. The terms of relationship used in three[18] of the chief languages spoken by the people of South India are exactly such as would follow from the cross-cousin marriage. In Tamil[19] the mother’s brother, the father’s sister’s husband, and the father of both husband and wife are all called _mama_, and this term is also used for these relatives in Telegu. In Canarese the mother’s brother and the father-in-law are both called _mava_, but the father’s sister’s husband fails to fall into line and is classed with the father’s brother.