The hormone
might conceivably modify the germ-plasm but if so, it would more likely
be in some wholly different way.
In general, we may confidently say that there is neither theoretical
necessity nor adequate experimental proof for belief that the results of
use and disuse are inherited.
(4) When we come to consider whether the effects of the environment are
inherited, we attack a stronghold of sociologists and historians.
Herbert Spencer thought one of the strongest pieces of evidence in this
category was to be found in the assimilation of foreigners in the United
States. "The descendants of the immigrant Irish," he pointed out, "lose
their Celtic aspect and become Americanised.... To say that 'spontaneous
variation,' increased by natural selection, can have produced this
effect, is going too far." Unfortunately for Mr. Spencer, he was basing
his conclusions on guesswork. It is only within the last few months that
the first trustworthy evidence on the point has appeared, in the careful
measurements of Hrdlicka who has demonstrated that Spencer was quite
wrong in his statement. As a fact, the original traits persist with
almost incredible fidelity. (Appendix C.)
In 1911, Franz Boas of Columbia University published measurements of the
head form of children of immigrants[14] which purported to show that
American conditions caused in some mysterious manner a change in the
shape of the head.
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