Ancestral relationships within and between districts in the region of Reading, England, as estimated by isonymy.

The distribution of surnames and the Coefficient of Relationship by Isonyny (Ri—a measure of commonality of surnames in two lists) have been determined for nine districts in and around Reading, Berkshire, from a list of 4,794 persons married there in 1972-1973. Ri was also calculated within 8 communities within the dis­tricts.The within-community Ri are slightly higher than those within districts. The within-district Ri are also slightly higher than those between districts. Pairs of districts contribute significantly to variance. There is also a tendency for males to show higher and more variable values of Ri than females. Marital mobility data show that in Reading and its urban field individuals are not bound to their immediate environs when selecting a mate. Hence the within- district Ri (mean = 57.1) is only slightly higher than that between districts (mean = 49.2). Compared with some rural regions, the variation is low. In Reading and its environs there is relatively little differentiation in the pattern of biological interrela­tionships as seen in the distribution of surnames