Generation is
conceived as a direct chain: the body produces the germ-cell which
produces another body which in turn produces another germ-cell, and so
on.
But a generation ago this idea fell under suspicion. August Weismann,
professor of zooelogy in the University of Freiburg, Germany, made
himself the champion of the new idea, about 1885, and developed it so
effectively that it is now a part of the creed of nearly every
biologist.
Weismann caused a general abandonment of the idea that the germ-cell is
produced by the body in each generation, and popularized the conception
of the germ-cell as a product of a stream of undifferentiated
germ-plasm, not only continuous but (potentially at least) immortal.
The body does not produce the germ-cells, he pointed out; instead, the
germ-cells produce the body.
The basis of this theory can best be understood by a brief consideration
of the reproduction of very simple organisms.
"Death is the end of life," is the belief of many other persons than the
Lotus Eaters. It is commonly supposed that everything which lives must
eventually die. But study of a one-celled animal, an Infusorian, for
example, reveals that when it reaches a certain age it pinches in two,
and each half becomes an Infusorian in all appearance identical with the
original cell.
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