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muscle fiber. These facts seem to me to justify the conclusion which I reached in a former paper:

Just as the size of a nucleus in any given species is proportional to the volume of the general protoplasm, so the volume of its chromosomes is proportional to the volume of the nucleus. The number of chromosomes and their relative sizes are characteristic for each species, but the absolute size of chromosomes depends upon the size of the nucleus from which they come. Throughout the period of cleavage, as the cells and muclei grow smaller, the chromosomes also diminish in size. The view of Boveri that the chromosomes divide when they have grown to their original size before division, and that thereby a definite specific size of ihe chromosomes is maintained, finds no confirmation in the work of Erdmann, Schleip or myself; while the view of Koehler that the autonomy of the chromosomes may be extended to their growth, which is supposed to be independent of that of other cell constituents, is flatly contradicted by the facts.

During the cleavage stages at least, neither the nuclei as a whole nor the chromosomes double in volume at each successive division as is so often assumed. The total volume of the nuclei at the 70-cell stage of Crepidula plana is only 2.25 times their volume at the 2-cell stage. The