The germ-plasm : a theory of heredity / [A. Weismann] ; translated by W. Newton Parker and Harriet Rönnfeldt.

  • Weismann, August, 1834-1914.
Date:
1893
Catalogue details

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

Credit: The germ-plasm : a theory of heredity / [A. Weismann] ; translated by W. Newton Parker and Harriet Rönnfeldt. Source: Wellcome Collection.

    51/522 (page 21)
    INTRODUCTION. 21 case of the higher forms of life a large number of facts have now been accumulated which can be used for the purpose of theoretical analysis. Although the study of heredity is greatly complicated by amphimixis, this mingling of the hereditary tendencies of two parents, and even the process of sexual reproduction which accompanies it, afford us a much deeper insight into the actual processes of heredity than we could ever have obtained in any other way. We may thus hope in time to penetrate further into its nature by carrying out more detailed investigations of the phenomena. In order to do so, however, we must not forget that this form of reproduction is neither the only nor the original one, and that even in multicellular organisms reproduction is not necessarily connected with amphimixis ; it must also be borne in mind that so-called asexual {motiogonic) reproduction forms the basis of the amphigonic method. The fundamental phenomena of heredity had already shaped their course in the living world before the introduction of amphimixis, and have, therefore, no connection with amphigonic descent and the complications arising from it. This fact has often been overlooked or left out of consideration, and thus the solution of the problem of heredity has been rendered much more difficult. A whole series of the phenomena of heredity can be investigated theoretically without considering the complications arising from amphimixis, though, in point of fact, it is always a factor, and thus the problem to be solved is very considerably simplified. The natural course of such an investigation would be to pass from the simple to the complex, but it is not advisable at present to begin the study of heredity by a consideration of the simplest beings, and to ascend from the unicellular to the multicellular organisms. For besides the fact that we know nothing of the individual phenomena—such as the transmission of the in¬ dividual characters—in the lower forms, the principal reason for not following the ordinary course in this case is the fact that amphigonic reproduction, or the processes of fer¬ tilisation and the complicated development of multicellular organisms, affords us, as already stated, a deep insight into the processes of heredity. The same is true in this case as in almost all physiological processes,—investigation cannot pro¬ ceed from the simple to the more complex without taking into