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Updated: July 10, 2025
Thus each egg of the second generation receives chromosomes which have come directly from the first generation, and thus it will follow that each of these eggs will have identical properties with the egg of the first generation.
Whatever chemical forces may have accomplished, they never could have combined different bodies into linin, centrosomes, chromosomes, etc., which, as we have seen, are the basis of cell life.
Under such conditions as prevail just before a cell divides, the chromatic substance is broken up and reassembled in the form of rods called chromosomes. Curiously enough the number of rods is uniform for each species of animal, though different numbers are characteristic of different species; the characteristic number for man is twenty-four.
It is curious to note how different are these discoveries concerning differences in the number of chromosomes from the conception of Morgan that a mutation depends on a factor situated in a part of one chromosome. More copious details concerning mutations will be found in the publications cited.
Thus it comes that, even in the adult, every body cell is made up of chromosomes from each parent, and may hence inherit characters from each. The cell of an animal thus consists of three somewhat distinct but active parts the cell substance, the chromosomes, and the centrosome.
This sort of splitting thus doubles the number of chromosomes, but produces no differentiation of material. Final stage with two nucleii in which the chromosomes have again assumed the form of a network. The next step in the cell division consists in the separation of the two halves of the chromosomes.
Division is also the first stage in reproduction in the most complicated animal bodies. When a cell division takes place, the nucleus breaks up into a number of thread-like portions which are known as chromosomes. There are supposed to be 24 pairs, or 48, in the human cell.
The evidence concerning sex and sex-linked characters and the localisation of their factors in the chromosomes of the gametes has no bearing on the action of hormones. The facts concerning the action of hormones are beyond the scope of current conceptions of the action of factors or genes localised in the gametes and particularly in the chromosomes.
It is difficult to avoid the conclusion that the stouter character of the organs in this plant is causally connected with the increased number of chromosomes.
This and the following figures represent the process of fertilization of an egg. In the cells of the body of the animal to which this description applies there are four chromosomes This is true of all the cells of the animal except the sexual cells.
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