But
we need not therefore accept his theory of a germ-plasm so isolated
and independent as to be beyond control or influence by the
habits of the body. The importance of use and disuse, and the
transmissibility of their effects, would seem to supply a factor
essential to evolution. Weismann has done good service in
emphasizing the stability of the germ-plasm. Evolution is always
slow, and, for that very reason, sure.
If these conclusions are correct, they have an important practical
bearing. Struggle and effort are essential to progress. Not inborn
talent alone, but the use which one makes of it, counts in
evolution. The effects of use and disuse are cumulative. The
hard-fought battle of past generations becomes an easy victory in
the present, just because of the strength acquired and handed down
from the past struggle. Persistent variation toward evil is in time
weeded out by natural selection. And, while evil remains in the
world, we are to lay up stores of strength for ourselves and our
descendants by sturdily fighting it. But the effects of right living
through a hundred generations are not overcome by the criminal life
of one or two. Evil surroundings weigh more in producing criminals
than heredity, and their children are not irreclaimable.
The struggles and victories of each one of us encourage the rest.
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