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Page:Popular Science Monthly Volume 65.djvu/224

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THE POPULAR SCIENCE MONTHLY.

tion of species. He, too has not yet succeeded in analyzing and distinguishing from each other—what has been de Vries's merit—variability within the boundaries of constant species and mutability which does not fluctuate, but which by a sudden bound leads to the new species.

Much closer to this valuable discovery we find two students of the fossil-animal kingdom, two paleontologists, one of whom (Waagen), as long as twenty-five years ago, understood the importance of the phenomenon of mutation, even without the support which the series of de Vries's experiments would, of course, have afforded him, while the second (W. B. Scott, of Princeton) has most clearly expressed himself (American Journal of Science, 1894) that the formation of species by selection of fluctuating mutations, such as Wallace maintains, is rendered most improbable by what the fossil-animal world teaches us.

This world of fossil animals exhibits in certain regions of the earth, where the successive geological formations have been retained in undisturbed order, a similarly undisturbed ascending series. Far from finding in that series the divergent fluctuations which Bateson had accepted for so many animals, Scott has shown (and has strengthened his argument by referring to the results of many other paleontologists) that these fluctuations are indeed—though exceptionally—found among fossil animals as so many individual deviations (thus proving that also in that time the fluctuating variability existed within the limits of the species)—but he is at the same time convinced that this phenomenon has nothing to do with the slow modification of species, which takes a straight line and not a zigzag one.

Scott, although he was not at that time acquainted with de Vries's experimental evidence, staunchly holds to the idea that species have not grown out of the gradual selection of deviating individuals, but have appeared by mutation, by very small but sudden starts from one stage to the next.

We see before our eyes how the species of the deeper layers are gradually modified as we reach the higher layers; we find that all individuals simultaneously underwent this modification; in other terms, the phenomenon can hardly be described otherwise than by saying that the older species tends directly towards an aim, which the younger species that has descended from it has attained.

Many paleontologists even go so far as to admit a previously determined direction in gradual evolution. There is, of course, close affinity between such a predetermined direction in evolution and the teleological idea of design presiding at the creation of species. Clerical opponents of evolution may here have their chance of adapting the newest results in the study of that process to their personal principles.