An introduction to the study of heredity / by E.W. Macbride.

  • MacBride, E. W. (Ernest William), 1866-1940.
Date:
[1924]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: An introduction to the study of heredity / by E.W. Macbride. Source: Wellcome Collection.

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    then transpires that they are not cords but sheets of denser material traversing the fluid sap. When a nucleus divides into two the lines of chromatin contract, and become arranged in a number of bands called chromo somes. It is a most wonderful thing that whenever they can be counted these chromo somes appear in the same number in all the cells of the body when the nucleus divides. This number is typically the same for all members of the same species of animal, but varies from species to species. For reasons which will soon transpire it is termed the diploid number, and is denoted by the symbol 2x. The chromosomes continue to contract, and as they grow shorter and thicker the nucleo lus, if there is any, becomes dissolved in the cell sap and totally disappears, and a little later the nuclear wall is also dissolved and the nuclear sap mingles with the protoplasm. It has been proved in several cases that the material of the nucleolus is ejected from the nucleus into the protoplasm. Whilst these changes have been going on the centrosome, which lies outside the nuclear wall, has divided into two and the daughter centrosomes have moved away from each other, each of them producing round itself an “ aster ” with out-