h while investigating
whether mental excellencies may not also be.

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
they left home and lived 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:[33] "In some cases the resemblance of body and mind had
continued unaltered up to old age, notwithstanding very different
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 similarity of nature, in which such differences of external
circumstances as may be consistent with the ordinary conditions of the
same social rank and country do not create dissimilarity. Positive
evidence, such as this, can not be outweighed by any amount of negative
evidence."

Frederick Adams Woods has brought forward[34] a piece of more exact
evidence under this head. It is known from 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 pair 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 Dr. Woods got his material; for the grandchild
has been brought up at the court of the paternal grandfather, where he
ought to have gotten all his "acquirements," and has perhaps never even
seen his maternal grandparents, who therefore could not be expected to
impress their mental peculiarities on him by "contagion." When Dr. 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 largely responsible for one's mental
make-up.

4. _Persistence of unlike qualities regardless of sameness in the_
_environment._ This is the converse of the preceding proposition, but
even more c