Popular Science Monthly Volume 65.djvu/220

Exported from Wikisource on September 25, 2024

216

THE POPULAR SCIENCE MONTHLY.

which especially differs from those we have been studying, by the fact that even when artificially fertilized, with the utmost precautions, the mutation is not stable. The majority of its descendants belong to three groups: O. scintillans, O. oblonga, O. Lamarckiana. As compared with the wonderful stability which we encountered in the preceding mutations, the lability of this one—which at the same time seems to follow a certain law—is a most remarkable phenomenon, the origin and the significance of which have still to be traced.

We have now seen that for a number of years de Vries has been able, by his careful and skilful experiments, actually to witness the very process of the origin of species in nature. On the particular spot near Graveland, where he first noticed the process of mutation in nature, it had, of course, been going on even before his first observations. He here encountered, besides the O. Lamarckiana, a second species, the O. laivifolia, with which he also made experiments in the Amsterdam hortus, and which also produced numerous mutations, some of them identical with those obtained from O. Lamarckiana.

Especially important was the irrefutable demonstration of the fact that the process of mutation does not appear as one single specimen which gives rise to a constant variety, but that it again and again repeats itself in every generation in a certain percentage, and that absolutely the same 'mutants' appear—even though in varying quantities. The individual mutants thus find their chance of surviving considerably increased and, as soon as a slight change in the outward circumstances occurs, any mutation, which at the outset was in the minority as compared with the parent species, may slowly but surely become the majority. It is constantly getting a fresh supply from the parent species and, as soon as it shows itself better adapted to the circumstances, it may finally supplant the parent species entirely.

This struggle for existence does not occur between individuals of the same species, but between the mutations and the parent species. As long as the mutation has not appeared, there can be no question of the origin of a new species; the species is then constant, and only submitted to fluctuating variability, which can produce local races (not elementary species) under the constant cooperation (either artificial or natural) of selection, but which never leads to the formation of species. During a period of mutation a modification of the species is not always a necessary consequence; for in many cases the parent species will prove to be the fittest, and the mutations will then none of them be permanent.

The fact has been established by de Vries that in the natural life of a wild plant a series of phenomena occurs which justifies us in saying that he has made us see and actually touch the origin of species, whereas Darwin had made us understand it.

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Table of Contents

Title page

Popular Science Monthly Volume 65.djvu/220

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