Volume 1

Essays upon heredity and kindred biological problems / by August Weismann ; edited by Edward B. Poulton, Selmar Schönland, and Arthur E. Shipley, authorized translation.

  • Shipley A. E. (Arthur Everett), Sir, 1861-1927.
Date:
1891-1892
Catalogue details

Licence: Public Domain Mark

Credit: Essays upon heredity and kindred biological problems / by August Weismann ; edited by Edward B. Poulton, Selmar Schönland, and Arthur E. Shipley, authorized translation. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    205/502 (page 187)
    IV.] FOUNDATION OF A THEORY OF HEREDITY. 187 formed, and I have defended this opinion for some years past ^, although I have hitherto laid especial stress on the positive aspect of the question, viz. on the continuity of the germ-plasm. I have attempted to prove that the germ-cells of an organism derive their essential nature from the fact that the germ-plasm of each generation is carried over into that which succeeds it; and I have tried to show that during the development of an egg into an animal, a part of the germ-substance—although only a minute part—passes over unchanged into the organism which is undergoing development, and that this part represents the basis from which future germ-cells arise. In this way it is to a certain extent possible to conceive how it is that the complex molecular structure of the germ-plasm can be retained unchanged, even in its most minute details, through a long series of generations. But how would this be possible if the germ-plasm were formed anew in each individual by the transformation of somatic idio-plasm ? And yet if we reject the ' continuity of the germ-plasm' we are compelled to adopt this latter hypo- thesis concerning its origin. It is the hypothesis adopted by Strasburger, and we have therefore to consider how the subject presents itself from his point of view. I entirely agree with Strasburger when he says, 'The specific qualities of organisms are based upon nuclei;' and I further agree with him in many of his ideas as to the relation between the nucleus and cell-body: 'Molecular stimuli proceed from the nucleus into the surrounding cytoplasm; stimuli which, on the one hand, control the phenomena of assimilation m the cell, and, on the other hand, give to the growth of the cytoplasm, which depends upon nutrition, a certain character peculiar to the species.' ' The nutritive cytoplasm assimilates, while the nucleus controls the assimilation, and hence the substances assimilated possess a certain constitution and nourish in a certain manner the cyto-idioplasm and the nuclear idioplasm. In this way the cytoplasm takes part in the phenomena of construction, upon which the specific form of the organism depends. This constructive activity of the cyto- idioplasm depends upon the regulative influence of the nuclei.' ^ This opinion was first expressed in my lecture, ' Ueber die Dauer des -Lebens, Jena, 1882, translated as the first essay in the present volume.