Essays upon heredity and kindred biological problems / by August Weismann ; authorized translation edited by Edward B. Poulton, Selmar Schönland and Arthur E. Shipley.

  • Weismann, August, 1834-1914.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Essays upon heredity and kindred biological problems / by August Weismann ; authorized translation edited by Edward B. Poulton, Selmar Schönland and Arthur E. Shipley. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

    140/476 (page 124)
    complete separation of the Magosphaera-ce[\s proves that their in- dividuality has not been completely subordinated to that of the whole colony, and it proves that the latter is not completely individualised 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 re- production of the single cells had taken place After this had been accomplished, Götte considers that death would consist ' in the complete separation of the cells from one another, aeeomj)anied 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 re- juvenescence, which Götte considers to be the essential part of encystment. Götte ought not to identify death with the dissolu- tion of the cell-colony of which the lowest and highest Poly- plastides 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 rejuve- nescence 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 rejuve- nescence 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 ' 1. c, p. 78. ^ 1. c, p. 47.