It certainly offers no explanation.
Flood-tide is not due to the interaction of particles of water,
though this may influence the form of the waves.
The centre of control is therefore not to be sought in individual
cells, whether germ-cells or somatic, but in the organism. And it is
the whole organism, one and indivisible, which controls in germ,
embryo, and adult, in egg and owl. This individuality, or whatever
you will call it, impresses itself upon developing somatic cells,
moulding them into appropriate organs, and upon germ-cells in
process of formation, moulding them so that they may continue its
sway. The muscle, modified by use or disuse, is a better expression
of the individuality of its possessor, and the same individuality
moulds similarly and simultaneously the germ-cells. Both are
different expressions or manifestations of the same individuality.
Only slowly does the individuality mould the muscles and nerves of
the adult body to its use. Still more slow may be the moulding of
the still more refractory germ-plasm, if such there be. But the
moulding process goes on parallel in the two cases.
But Weismann's argument rests not merely upon any difficulty or
impossibility of the transmissibility of acquired characteristics.
His argument is rather that all facts can be better explained by his
theory without postulating or accepting such transmission, cases of
which have never been absolutely proven.
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