As the children of this school commonly enter at a very early age, and as the staff and the methods of teaching remain very constant, we have in the case of the 180 brothers and sisters included in the 600 children closely similar school training. Mr. Earle measured the ability of any individual by his deviation from the average for his grade and sex, and found the co-efficient of correlation between children of the same family to be .50. That is, any individual is on the average fifty per cent as much above or below the average for his age and sex as his brother or sister. Similarities in home training might theoretically account for this, but any one experienced in teaching will hesitate to attribute much efficacy to such similarities. Bad spellers remain bad spellers though their teachers change. Moreover, Dr. J. M. Rice in his exhaustive study of spelling ability found little or no relationship between good spelling and any one of the popular methods, and little or none between poor spelling and foreign parentage. Yet the training of a home where parents do not read or spell the language well must be a home of relatively poor training for spelling. Cornman's more careful study of spelling supports the view that ability to spell is little influenced by such differences in school or home training as commonly exist.[1] [Footnote 1: Thorndike: _loc. cit._, p. 78.] In general the influence of heredity may be said far to outweigh the influence of home training. In all the cases reported, the resemblances were about the same in traits subject to training, and in those not subject to training. Thus industry and conscientiousness and public spirit, which are clearly affected by environment, show no greater resemblance than such practically unmodifiable traits as memory, original sensitiveness to colors, sounds, and distances. The influence of parentage, it must be added, consists in the transmission of specific traits, not of a certain "nature" as a whole. There are in the germ and the ovum which constitute the inheritance of each individual, certain determinant elements. The elements that determine the original traits with which each individual will be born vary, of course, in the germs produced by a single parent less than among individuals chosen at random, but they vary none the less. In this variation of the determining elements in the germs of the same individual is to be found the cause of the variation in the physical and mental traits among children of the same parents. Since the determining elements, the unit characters that appear in the sperm or ovum of each individual, do not appear uniformly even in children of the same parents, brother and sister may resemble each other in certain mental traits, and differ in others. "A pair of twins may be indistinguishable in eye color and stature, but be notably different in hair color and tests of intellect."