Powerful corroborative evidence is supplied by a second series of facts. Among the Omaha, where descent is reckoned in the paternal line, the father’s sister’s daughter is no longer classed with the father’s sister but with the sister’s daughter. These, it may be noted incidentally, would belong to the same division if the moieties of the Omaha were at one time exogamous, for which there is some evidence. But the essential point is that here the mother’s brother’s son and all his male descendants through males are indiscriminately classed with the maternal uncle. It is clear that they are all members of the same gens, and corresponding to our Hidatsa experiment we find that as soon as we pass outside the gens the terminology changes: my mother’s brother’s _daughter’s_ son is not my maternal uncle but my brother since his mother, the uncle’s daughter, is called ‘mother’, belonging as she must to my mother’s gens.[49] The Omaha phenomena are absolutely paralleled not only among other Southern Siouans but also among a number of Algonquians, _viz._, the Miami, Sauk and Fox, Kickapoo, Menomini and Shawnee. The area covered is an absolutely continuous one, and it is impossible not to explain such a distribution by diffusion. This conclusion is accentuated by the fact that the Ojibwa, though an Algonquian people with a gentile system, do not share the Omaha variant of the Dakota scheme but conform to the more usual type found among their neighbors, the Dakota. The mere presence of a gentile organization, though doubtless a favorable basis for the development or adoption of the Omaha scheme, is not the only determining condition; the presence of terminological features in a particular tribe is also a function of its geographical position or historical connections. This does not interfere with the ultimate interpretation of such features but it shows the necessity of taking into account the geographico-historical situation. At present I cannot suggest what may have been the differential condition that produced the Hidatsa variant among some tribes with a clan system but not among the Iroquois; or the Omaha variant among certain Algonquian tribes but not the Ojibwa.