Volume 2

The collected papers of Charles Darwin / edited by Paul H. Barrett ; with a foreword by Theodosius Dobzhansky.

  • Charles Darwin
Date:
1977
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The collected papers of Charles Darwin / edited by Paul H. Barrett ; with a foreword by Theodosius Dobzhansky. Source: Wellcome Collection.

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    concealment from their enemies would inevitably survive the longest. We have also here an acting cause to account for that balance so often observed in nature,—a deficiency in one set of organs always being compensated by an increased development of some others—powerful wings accompanying weak feet, or great velocity making up for the absence of defensive weapons; for it has been shown that all varieties in which an unbalanced deficiency occurred could not long continue their existence. The action of this principle is exactly like that of the centrifugal governor of the steam engine, which checks and corrects any irregu larities almost before they become evident; and in like manner no unbalanced deficiency in the animal kingdom can ever reach any con spicuous magnitude, because it would make itself felt at the very first step, by rendering existence difficult and extinction almost sure soon to follow. An origin such as is here advocated will also agree with the peculiar character of the modifications of form and structure which obtain in organized beings—the many lines of divergence from a central type, the increasing efficiency and power of a particular organ through a succession of allied species, and the remarkable persistence of un important parts such as colour, texture of plumage and hair, form of horns or crests, through a series of species differing considerably in more essential characters. It also furnishes us with a reason for that “more specialized structure which Professor Owen states to be a characteristic of recent compared with extinct forms, and which would evidently be the result of the progressive modification of any organ applied to a special purpose in the animal economy. We believe we have now shown that there is a tendency in nature to the continued progression of certain classes of varieties further and further from the original type—a progression to which there appears no reason to assign any definite limits—and that the same principle which produces this result in a state of nature will also explain why domestic varieties have a tendency to revert to the original type. This progression, by minute steps, in various directions, but always checked and balanced by the necessary conditions, subject to which alone existence can be preserved, may, it is believed, be followed out so as to agree with all the phenomena presented by organized beings, their extinction and succes sion in past ages, and all the extraordinary modifications of form, instinct, and habits which they exhibit. Temate, February, 1858 1. [Read 1 July 1858.] Charles Darwin and Alfred Wallace. Communicated by Charles Lyell and J. D. Hooker. Journal of the Proceedings of the Linnean Society (Zoology) 3 (1859): 45-62.t 2. This MS. work was never intended for publication, and therefore was not written whh care.—C. D. 1858.