1.1 _ NTECEDFXT~,. 3.3
between close harmony and wide contrast, inn which sexual instinct acts most powerfully ? It appears from the facts in this chapter, that the marriages of parents of the scientific men on my list actually tended to produce differentiation and purity of race. My data concerning the parents of men of other groups are insufficient to enable me yet to give comparative results showing how far the selective sexual instincts of the population generally would thwart, be indifferent to, or co-operate with the influences of future social restrictions on unsuitable marriages, or encouragement of suitable ones.
The following statement shows, in percentages, the position of the scientific men in respect to age among their brothers and sisters:
Only sons, 22 cases ; eldest sons,. 26 cases ; youngest sons, 1.5 cases. Of those who are neither eldest nor youngest, 13 come in the elder half of the family ; 12 in the younger half ; and 11 are exactly in the middle. Total, 99.
It further appears that, at the time of the