se unmated individuals differ in any
important respect from the married part of the population, preferential
mating will be evident.

[Illustration: INTELLIGENT GIRLS ARE MOST LIKELY TO MARRY

FIG. 33.--Graph showing the marriage-rate (on the same scale as
in Fig. 32) of the graduates of a normal school, as correlated with
their class standing. The girls who received the highest marks in their
studies married in the largest numbers. It is evident that, on the
whole, girls who make a poor showing in their studies in such schools as
this are more likely to be life-long celibates than are the bright
students.]

At the extremes, there is no difficulty in seeing such mating. Certain
men and women are so defective, physically, mentally, or morally, as to
be unable to find mates. They may be idiots, or diseased, or lacking
normal sexuality, or wrongly educated.

But to get any adequate statistical proof of preferential mating on a
broad scale, has been found difficult. Two small but suggestive studies
made by Miss Carrie F. Gilmore of the University of Pittsburgh are
interesting, though far from conclusive. She examined the records of
the class of 1902, Southwestern State Normal School of Pennsylvania, to
find which of the girls had married. By means of photographs, and the
opinions of disinterested judges, the facial appearance of all the girls
in the class was graded on a scale of 100, and the curve in Fig. 32
plotted, which shows at a glance just what matrimonial advantage a
woman's beauty gives her. In general, it may be said that the prettier
the girl, the better her chance of marriage.

[Illustration: YEARS BETWEEN GRADUATION AND MARRIAGE

FIG. 34.--Curve showing period that elapsed between the
graduation of women at Washington Seminary (at the average age of 19
years) and their marriage. It includes all the graduates of the classes
of 1841 to 1900, status of 1913.]

Miss Gilmore further worked out the marriage rate of these normal school
girls, on the basis of the marks they obtained in their class work, and
found the results plotted in Fig. 33. It is evident that the most
intelligent girls, measured by their class standing, were preferred as
wives.

[Illustration: THE EFFECT OF LATE MARRIAGES

FIG. 35.--Given a population divided in two equal parts, one of
which produces a new generation every 25 years and the other every
33-1/3 years, the diagram shows that the former group will outnumber the
latter two to