THE
EVOLUTION THEORY
VOLUME I
THE
EVOLUTION THEORY
BY
Dr. AUGUST WEISMANN
PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF FREIBURG IN BREISGAU
TRANSLATED WITH THE AUTHOR'S CO-OPERATION
BY
J. ARTHUR THOMSON
REGIUS PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF ABERDEEN
AND
MARGARET R. THOMSON
ILLUSTRATED
IN TWO VOLUMES
VOL. I
LONDON
EDWARD ARNOLD
41 & 43 MADDOX STREET, BOND STREET, W.
1904
All rights reserved
AUTHOR'S PREFACE
When a life of pleasant labour is drawing towards a close,the wish naturally asserts itself to gather together the mainresults, and to combine them in a well-defined and harmoniouspicture which may be left as a legacy to succeeding generations.
This wish has been my main motive in the publicationof these lectures, which I delivered in the University ofFreiburg in Breisgau. But there has been an additionalmotive in the fact that the theory of heredity publishedby me a decade ago has given rise not only to many investigationsprompted by it, but also to a whole literatureof 'refutations,' and, what is much better, has brought tolight a mass of new facts which, at first sight at least, seemto contradict my main theory. As I remain as convincedthat the essential part of my theory is well grounded asI was when I first sketched it, I naturally wish to show howthe new facts may be brought into harmony with it.
It is by no means only with the theory of heredity byitself that I am concerned, for that has served, so to speak,as a means to a higher end, as a groundwork on which tobase an interpretation of the transformations of life throughthe course of the ages. For the phenomena of heredity, likeall the functions of individual life, stand in the closestassociation with the whole evolution of life upon our earth;indeed, they form its roots, the nutritive basis from which allits innumerable branches and twigs are, in the long run,derived. Thus the phenomena of the individual life, andespecially those of reproduction and inheritance, must beconsidered in connexion with the Theory of Descent, thatthe latter may be illumined by them, and so brought nearerour understanding.
I make this attempt to sum up and present as a harmonious[Pg vi]whole the theories which for forty years I have been graduallybuilding up on the basis of the legacy of the great workers ofthe past, and on the results of my own investigations andthose of many fellow workers, not because I regard the pictureas complete or incapable of improvement, but because I believeits essential features to be correct, and because an eye-troublewhich has hindered my work for many years makes ituncertain whether I shall have much more time and strengthgranted to me for its further elaboration. We are standingin the midst of a flood-tide of investigation, which is ceaselesslyheaping up new facts bearing upon the problem of evolution.Every theory formulated at this time must be preparedshortly to find itself face to face with a mass