and physical
traits, and generally speaking, belong to different types, it is very
improbable that there would be any ill effects resulting from the mere
fact of consanguinity. A case in point is furnished me by a
correspondent. A first cousin marriage which turned out exceedingly
well was between strongly contrasted individuals; the husband was
"short, stocky and dark complexioned" while the wife was "tall, slight
of figure, and of exceedingly light complexion." In other cases in
which the results were not so good the husband and wife bore a close
resemblance to one another, physically and mentally.

This, however, does not agree with the results obtained by Professor
Karl Pearson. Basing his conclusions on the correlation of stature
between husband and wife, he believes that homogamy is a factor of
fertility. Taking 205 marriages from Mr. Francis Galton's _Family
Records_, Professor Pearson found the correlation between husband and
wife to be .0931 +- .0467, while weighted by their fertility the
correlation was .1783 +- .0210, practically doubling the intensity of
assortative mating.[100] The value of these correlations, however, is
impaired, as he says, by the insufficient number of observations, and
by the fact that absolutely taller mothers are the more fertile.

[Footnote 100: _Royal Society Proceedings_, vol. 66, p. 30.]

In a subsequent investigation of from 1000 to 1050 pairs of parents of
adult children, Professor Pearson found the correlation in stature to
be .2804 +- .0189; of span .1989 +- .0204; and of forearm .1977 +- .0205;
with cross coefficients varying from .1403 to .2023. If, as he
believes, "The parents of adult children are on the average more alike
than first cousins, then it follows that any evils which may flow from
first cousin marriage depend not on likeness of characters, but on
sameness of stock."[101]

[Footnote 101: _Biometrika_, vol. ii, p. 373.]

But even if it were true, as is very improbable, that parents of adult
children are more alike than first cousins, it would still be likely
to follow that first cousins who married would be more alike than
first cousins in general. A certain degree of resemblance is
undoubtedly necessary to complete fertility: husband and wife must be
physically compatible, and must both enjoy a certain degree of health
and physical strength. These facts are admitted by all, but it does
not follow that resemblance beyond a certain point is not in itself
de