Page:Popular Science Monthly Volume 43.djvu/492

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something which it is "easy to imagine," but he assumes something which it is difficult to imagine; and apparently thinks that a scientific conclusion may be thereupon safely based.

But now to what end are we asked to make a gratuitous "supposition," to accept as true something strange which is "quite conceivable," and to strain our imaginations without the slightest aid from the evidence? Simply to save Prof. Weismann's hypothesis—to shelter it against a great body of adverse facts. When we have recognized the truth that what he regards as a primary division of labor is no division of labor at all—when we see that the corollary he draws respecting the implied primary differentiation of reproductive cells from somatic cells is consequently without warrant; we have no occasion to feel troubled that his deductive conclusion is inductively disproved. We are not dismayed on finding that throughout vast groups of organisms there is shown no such antithesis as his theory requires. And we need not do violence to our thoughts in explaining away the contradictions.

Associated with the assertion that the primary division of labor is between the somatic cells and the reproductive cells, and associated with the corollary that the primary differentiation is that which arises between them, there goes another corollary. It is alleged that there exists a fundamental distinction of nature between these two classes of cells. They are described as respectively mortal and immortal, in the sense that those of the one class are limited in their powers of multiplication, while those of the other class are unlimited. And it is contended that this is due to inherent unlikeness of nature.

Before inquiring into the truth of this proposition, I may fitly remark upon a preliminary proposition set down by Prof. Weismann. Referring to the hypothesis that death depends "upon causes which lie in the nature of life itself," he says:

"I do not however believe in the validity of this explanation; I consider that death is not a primary necessity, but that it has been secondarily acquired as an adaptation. I believe that life is endowed with a fixed duration, not because it is contrary to its nature to be unlimited, but because the unlimited existence of individuals would be a luxury without any corresponding advantage" (p. 24).

This last sentence has a teleological sound which would be appropriate did it come from a theologian, but which seems strange as coming from a man of science. Assuming, however, that the implication was not intended, I go on to remark that Prof. Weismann has apparently overlooked a universal law of evolution—not organic only, but inorganic and superorganic—which implies the necessity of death. The changes of every aggre-