458 The Journal 
be personally defective, part of their 
offspring will be affected. 
This production of sound children 
from an unsound parent, in the first 
case, and unsound children from two 
apparently sound parents in the second 
case, 1s exactly the opposite of what 
we should expect if the child gets his 
unsoundness merely by imitation or 
“contagion.” The difference cannot 
reasonably b> explained by any differ- 
ence in enviro.ment or external stimuli. 
Heredity ofiers a satisfactory explana- 
tion, for some forms of feeblemindedness 
and epilepsy, and some of the diseases 
known as insanity behave as recessives 
and segregate in just the way mentioned. 
We can show abundant analogies in the 
inheritance of other traits in man, 
lower animals, and plants, that behave 
in exactly the same manner. 
So far as I am aware, no psychologist 
has yet come forward to ‘“‘demonstrate’’ 
that feeblemindedness is due to a sub- 
conscious complex formed in childhood, 
instead of to heredity, but some of 
them appear to be moving in that 
direction. No one would allege that 
all mental defect is due to inheritance; 
perhaps only a small part is, although 
all data now available indicate that the 
part isa majority. But there are many 
cases in which the heredity factor can 
hardly be denied without stultification; 
and if mental defects are inherited, 
then it is worth while investigating 
whether mental excellences may not be. 
EVIDENCE FROM TWINS 
-3. The persistence of like qualities 
regardless of difference in environment. 
Any parent with open eyes must see 
this in his own children—must see that 
they retained the inherited traits even 
when living under entirely different 
surroundings. But the histories of 
twins furnish the most graphic evidence. 
Galton, who collected detailed histories 
of thirty-five pairs of twins who were 
closely alike at birth, and examined 
their history in after years, writes,® 
‘In some cases the resemblance of body 
and mind had continued unaltered up 
® Galton, Francis. 
7 Woods, Frederick Adams. 
8 Op. cit., pp. 170-171. 
Inquiries into Human Faculty, p. 167. 
Heredity in Royalty. 
of Heredity 
to old age, notwithstanding very dif- 
ferent conditions of life,’’ in other cases 
where some dissimilarity developed, it 
could be traced to the influence of an 
illness. Making due allowance for the 
influence of illness, yet “‘instances do 
exist of an apparently thorough simi- 
larity of nature, in which such differ- 
ence of external circumstances as may 
be consistent with the ordinary condi- 
tions of the same social rank and country 
do not create dissimilarity. Positive 
evidence, such as this, cannot be out- 
weighed by any amount of negative 
evidence.” 
Dr. Frederick Adams Woods has 
brought forward’ a piece of more exact 
evidence under this head. We know 
by many quantitative studies that, in 
physical heredity, the influence of the 
paternal grandparents and the influence 
of the maternal grandparents is equal; 
on the average one will contribute no 
more to the grandchildren than the 
other. If mental qualities are due 
rather to early surroundings than to 
actual inheritance, this equality of 
grandparental influence is incredible in 
the royal families where Woods got his 
material; for the grandchild has been 
brought up at the court of the paternal 
grandfather, where he ought to have 
got all his “‘acquirements,”’ and has per- 
haps never even seen his maternal 
grandparents, who therefore could not 
be expected to impress their mental 
peculiarities on him by “contagion.” 
When Woods actually measured the 
extent of resemblance to the two sets 
of grandparents, for mental and moral 
qualities, he found it to be the same in 
each case: as is inevitable if they are 
inherited, but as is incomprehensible if 
heredity is not responsible for one’s 
mental makeup. 
ENVIRONMENT IS POWERLESS 
4. Persistence of unlike qualities re- 
gardless of sameness in the environment. 
This is the converse of the preceding 
proposition, but even more convincing. 
Here again, I quote Galton,* with a 
London, 1907. 
New York, 1906. 
