It seems hardly reasonable to suppose that a
material of this sort should be exposed, in the higher animals at least,
to all the vicissitudes of the environment, and to injury or change from
the chance of outward circumstances.
In spite of these presumptions which the biologist would, to say the
least, consider worthy of careful investigation, the world is full of
well-intentioned people who are anxious to improve the race, and who in
their attempts to do so, wholly ignore the germ-plasm. They see only the
body-plasm. They are devoted to the dogma that if they can change the
body (and what is here said of the body applies equally to the mind) in
the direction they wish, this change will in some unascertainable way be
reproduced in the next generation. They rarely stop to think that man is
an animal, or that the science of biology might conceivably have
something to say about the means by which his species can be improved;
but if they do, they commonly take refuge, deliberately or
unconsciously, in the biology of half a century ago, which still
believed that these changes of the body could be so impressed on the
germ-plasm as to be continued in the following generation.
Such an assumption is made to-day by few who have thoroughly studied the
subject.
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