Heredity : in the light of recent research / by L. Doncaster.
- Doncaster, L. (Leonard), 1877-1920.
- Date:
- 1910
Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Credit: Heredity : in the light of recent research / by L. Doncaster. Source: Wellcome Collection.
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![I] HEREDITY 123 somes must occur, either by elimination of complete chromosomes or by transverse instead of longitudinal splitting, before any complete observations had been made showing that this actually happens. Since Weismann supposes that the germ-plasm is contained in the chromosomes of the germ-cells, and since half the chromosomes are removed in the 'maturation' of these cells without preventing the transmission of any part to the offspring by inherit¬ ance, he concluded that each chromosome contains all the units (' determinants ') necessary to a complete individual. (Later work has rendered this conclusion doubtful : see Appendix ii.) When fusion of male and female sex-cells takes place, the resulting individual will contain a mixture of the parental germ-plasms, the paternal in some chromosomes, the maternal in others. In the maturation of the sex-cells half these germ-plasms will be removed and in the next generation a fresh mixture will take place. It thus follows that the different chromosomes contain germ- plasms descended from different ancestors, and different mixtures of these will occur in different individuals. Here then we come to Weismann's hypothesis of the origin of variation. Since different individuals contain different combinations of an¬ cestral germ-plasms, these will lead to varying effects in the development of the body ; new com¬ binations will be continually occurring in every](https://iiif.wellcomecollection.org/image/b18030117_0140.JP2/full/800%2C/0/default.jpg)
