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
Nothing can be said against this, if we agree in identifying death with
the encystment of the Monoplastides. Now we could, as Götte rightly
remarks, derive the lower forms of Polyplastides from _Magosphaera_ if
‘the connection between the cells of the ciliated sphere were retained
until encystment, viz. until the reproduction of the single cells had
taken place[70].’ After this had been accomplished, Götte considers
that death would consist ‘in the complete separation of the cells from
one another, accompanied in all probability by their simultaneous
change into germ-cells.’ The fallacy in this is evident; if death is
represented in one case by the encystment during which single cells
change into germ-cells, then this must apply to the other case also,
for nothing has changed except the duration of the cell-colony. The
nature of encystment cannot be affected by the fact that the cells
separate from one another a little earlier or a little later. If it is
true that death is represented by encystment among the Monoplastides,
then the same conclusion must also hold for the Polyplastides; or
rather death must be represented in them by the process of
rejuvenescence, which Götte considers to be the essential part of
encystment. Götte ought not to identify death with the dissolution of
the cell-colony of which the lowest and highest Polyplastides are alike
composed; but he should seek it in the process of rejuvenescence which
takes place within the germ-cells. If it is essential to the nature of
reproduction that the cells set apart for that purpose should pass
through a process of rejuvenescence, which is equivalent to death, then
this must be true for the reproductive cells of all organisms. If these
conclusions hold good, there is nothing to prevent us from assuming
that such a process of rejuvenescence actually occurs in the higher
animals. Götte evidently holds this view, as is plainly shown in the
last pages of his essay. He there attempts to bring his views of the
death and rejuvenescence of the germ into harmony with his previously
developed idea of the derivation of death among the Polyplastides from
the dissolution of the cell-colonies. Götte still clings to the view
which he propounded in describing the development of _Bombinator_,
according to which the egg-cell of the higher Metazoa must pass through
a process of rejuvenescence representing death, before it can become a
germ.
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