For while Darwin emphasized natural selection, he
accepted to a certain extent the transmission of special effects of
use and disuse.
A special theory of heredity, pangenesis, has been accepted by many
of the Neo-Lamarckian school. The theory of pangenesis, as
propounded by Mr. Darwin, may be very briefly stated as follows: The
cells in all parts of the body are continually throwing off germinal
particles, or "gemmules." These become scattered through the body,
grow, and multiply by division. On account of mutual attraction they
unite in the reproductive glands to form eggs or spermatozoa. The
germ-cells are thus the bearers of heredity because they contain
samples, so to speak, of all the organs of the body.
In heredity, according to Weismann's theory, the egg is the centre
of control, the continuous germ-plasm the source of all transmitted
changes; according to Darwin's theory, the body is the source, and
the egg is derived in great part at least from it. If you put to the
two the time-honored question, Which is first, the owl or the egg?
Weismann would announce, with emphasis, The egg; Darwin would say,
The owl. One proposition is the converse of the other, and most
facts accord almost equally well with both theories.
In any family, devoted for generations to literary or artistic
pursuits, the children show, as a rule, an aptitude for such
pursuits not manifested by those of other families.
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