IIo THE TREND OF THE RACE 
While it is recognized by nearly all competent students that 
mental ability is inherited, the precise method of its inheritance is 
not thoroughly established. Heritable characteristics present 
very different amounts of purely somatic or fluctuating varia- 
bility and it would seem not improbable a priori that superior 
mental endowments depending, as they do, upon the delicate and 
intricate organization of the brain may be subject to such varia- 
bility to an unusual degree. A child of good ancestry but exposed 
while in utero to the influence of malnutrition, alcohol, or the 
toxins of disease at the time when the delicate architecture of its 
brain is being built up may fall considerably short of its normal 
expectation in intellectual development. But notwithstanding its 
intricate structure and the apparent ease with which the delicate 
balance of its organization might be upset, the nervous system is 
reproduced in successive generations with a remarkable degree 
of fidelity, both as regards its external connections and its internal 
mechanism. Possibly the fluctuating variations in the nervous 
system may be in part responsible for the fact that the parent- 
offspring and fraternal correlations in the inheritance of mental 
traits are usually found to be somewhat below those observed 
for various physical characters. But there are other reasons 
which might plausibly be assigned also. Although fluctuating 
variability may affect the basis of mentality somewhat more than 
it affects eye color or cephalic index it is not sufficient greatly to 
obscure the facts of mental inheritance, or to reduce very mark- 
edly the coefficients of mental resemblance between near relatives. 
Is the inheritance of mental traits in accordance with Men- 
del’s law? The question is one of peculiar difficulty since mental 
traits, as a rule, do not present the sharply definable and discrete 
features that often characterize the physical peculiarities of the 
body. Common observation, however, yields abundant evidence 
of the alternative inheritance of mental characteristics. Almost 
every family includes children with different aptitudes, disposi- 
tions, and tastes that manifest themselves from early infancy. 
In their mental characteristics children resemble now the father, 
now the mother or some grandparent or other relative. Many 
