On the Origin of Mutations

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Abstract
The present tendency of biologists to regard the chromosomes as the only, or chief, constituents of the cell upon which agents may act to produce mutations is criticized. Various factors, such as fragmentation of the egg, changing its temp. or chemical environment, or even subjecting it to certain radiations, can not be shown directly to affect the chromatin, though the latter may subsequently register evidences of alteration; rather is it clear that these factors, at least initially, cause changes in the cytoplasm, particularly in its cortical layer. Thus even the classical experiments of Boveri on dispermic fertilization, and of Baltzer on cross-fertilization, are dependent on first injuring the cytoplasm in order that the abnormal types of fertilization and subsequent chromosomal derangement may be brought about. X-rays seem to affect the chromosomes, but it is difficult to prove that they do not affect the cytoplasm first, and in the case of ultra-violet it sems certain that such is the case. The chromosomal aberrations may then be secondary. Likewise the normal mechanical behavior of the chromosomes may well be conditioned by cytoplasmic factors, in fact almost certainly so. The cell should be regarded as a unified reacting system in which environmental changes are first registered in the cortical cytoplasm.

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