Essays Upon Heredity and Kindred Biological Problems: Authorised TranslationWeismann, August
Science
Essays Upon Heredity and Kindred Biological Problems: Authorised Translation
Weismann, August
Evolution (Biology); Genetics; Reproduction
But even if we assume, that the death of the Orthonectides is, in
Götte’s sense, a consequence of reproduction, inasmuch as, in the two
forms of females as well as in the male, the extrusion of a mass of
developed germ-cells or embryos deprives the organism of the
physiological possibility of living longer, how can we explain the
necessity of death as a direct consequence of reproduction in all
Polyplastides? Is the body—the _soma_—of the Metazoa so imperfectly
developed, as compared with the reproductive cells, that the extrusion
of the latter involves the death of the former? As a matter of fact in
the majority of cases the relations are reversed; the number of
body-cells usually exceeds the germ-cells a hundred- or a
thousand-fold, and the body is, as regards nutrition, so completely
independent of the reproductive cells, that it need not be in the least
disadvantageously affected by their extrusion. And if the
Orthonectid-like ancestors of the Metazoa were compelled to give up
their insignificant somatic part after the extrusion of their
germ-cells, because it could now no longer support itself, does it
therefore follow that the somatic cells had for ever lost the power of
surviving, even when their phyletic descendants were surrounded by more
favourable conditions? Had they to inherit ‘the necessity of death’ for
all time? Whence came this great change in the nature of organisms
which, before the differentiation of Homoplastids into Heteroplastids,
were endowed with the immortality of unicellular beings?
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