The first, then, and most important element of heredity is that
there should be unbroken continuity, and hence sameness of
personality, between parents and offspring, in neither more nor less
than the same sense as that in which any other two personalities are
said to be the same. The repetition, therefore, of its
developmental stages by any offspring must be regarded as something
which the embryo repeating them has already done once, in the person
of one or other parent; and if once, then, as many times as there
have been generations between any given embryo now repeating it, and
the point in life from which we started--say, for example, the
amoeba. In the case of asexually and sexually produced organisms
alike, the offspring must be held to continue the personality of the
parent or parents, and hence on the occasion of every fresh
development, to be repeating something which in the person of its
parent or parents it has done once, and if once, then any number of
times, already.
It is obvious, therefore, that the germ-plasm (or whatever the fancy
word for it may be) of any one generation is as physically identical
with the germ-plasm of its predecessor as any two things can be.
The difference between Professor Weismann and, we will say,
Heringians consists in the fact that the first maintains the new
germ-plasm when on the point of repeating its developmental
processes to take practically no cognisance of anything that has
happened to it since the last occasion on which it developed itself;
while the latter maintain that offspring takes much the same kind of
account of what has happened to it in the persons of its parents
since the last occasion on which it developed itself, as people in
ordinary life take of things that happen to them.
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