trimental.

Professor Pearson's own experiments in this line, however, do not
give consistent results, for in correlating eyecolor with fertility,
heterogamy seems to increase fertility. The highest average fertility
(4.57) is in those cases where the father is dark-eyed and the mother
light-eyed, while the lowest is where both parents have blue-green or
gray eyes.[102]

[Footnote 102: _Phil. Trans. of the Royal Society_, vol. 195 A, p.
150.]

In a recent study an attempt has been made to measure the coefficient
of correlation between cousins.[103] In the characteristics of health,
success, temper and intelligence the coefficients ranged between .25
and .30. These values differ but little from those found to obtain for
the resemblance between avuncular relatives for eye color (.265), or
between grandparent and grandchild for the same characteristic
(.3164).[104] Positive results were also found, with one doubtful
exception, for the occurrence of insanity and tuberculosis in cousins.
The writer concludes: "The grandparent, the uncle and aunt, and the
cousin are on practically the same footing with regard to relationship
or intensity of kinship as measured by degree of likeness of
character; and it seems probable that any scientific marriage
enactments would equally allow or equally forbid marriage between
grandparent and grandchild, uncle and niece, aunt and nephew, and
between first cousins."[105]

[Footnote 103: Elderton and Pearson, "On the Measure of the
Resemblance of First Cousins." _Eugenics Laboratory Memoirs IV._
Reviewed in _Br. Med. Journal_, Feb. 15, 1908.]

[Footnote 104: _Phil. Trans. of the Royal Society_, vol. 195 A, p.
106.]

[Footnote 105: Elderton and Pearson, op. cit.]

As we should expect the resemblance between near relatives has been
found to be much greater. From a measurement of from 4000 to 4886
pairs, the average correlation of the characteristics of stature,
span, forearm length and eyecolor between parent and child was .4695.
By similar computations and measuring the same characteristics, the
fraternal correlation was found to be .508.[106] From measurements of
a greater variety of characteristics in school children the mean
fraternal correlation was .539.[107] In athletic power the coefficient
was still higher, .72 between brothers, .75 between sisters and
.49 between brothers and sisters. Measurements of mental
characteristics--vivacity, assertiveness, introspection, popularity,