For a clear understanding of the laws of heredity, it seems important to know whether a similar alternating inheritance occurs in marriages of members of the same type. I have been enabled to investigate this question by a study of the East European Hebrews living in New York. A simple consideration shows, that, if the children tend to follow a type intermediate between the type of their parents, then the children of one family will show the same degree of resemblance among themselves, no matter how great the difference between the parents; for, if they simply tend to reproduce a middle type, it would not make any difference whether the mother is excessively short and the father excessively tall, or whether both parents are of middle stature. In both of these cases the intermediate value would be the same, and we should therefore expect that the effect upon the children would be the same. If, on the other hand, there is any kind of alternation in inheritance, the effect upon the family would be quite different. We should expect, in a family of which both parents are near the typical average, to find the children also to be near this average. On the other hand, if the mother is excessively short and the father excessively tall, we should expect some of the children to follow the mother in regard to shortness of stature, others to follow the father in regard to tallness. It will therefore be seen that in the case of alternating inheritance, we must expect an increased variability among the children. The compilation of material obtained from several thousand families shows very definitely that the variability among children both of whose parents belong to the same racial type, even to the same local type, increases quite considerably with the increased difference of the parents; so that we may assume a decided tendency to alternating inheritance in these cases. There is, however, no evidence whatever of the dominance of one type over another.