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The numerous subsidiary theses interwoven in Weismann’s theory are entirely coherent, and have been thought out to their conclusions with praiseworthy determination.
But as to the meaning of this systematic relationship, whether it can be “explained” by descent, whether it has existed from all eternity, or how it has arisen, the experiment does not inform us. The same idea may be illustrated in regard to Weismann’s “predicting.” This, too, is a proof of evolution, but not of descent.
But they have at least the merit that they give a vivid impression of what is most plausible and attractive in the idea of descent, and moreover they have helped towards orientation in the discussion. Nor can we ignore the very marked taxonomic and architectonic talent which their construction displays. Weismann’s Evolutionist Position.
This opposition is most concretely and comprehensively expressed in Haacke’s “Gestaltung und Vererbung.” The infinitely complex intricacy of Weismann’s minute microcosm within the germ-cell, indeed within every id in it, is justly described as a mere duplication, a repetition in the infinitely little of the essential difficulties to be explained.
He criticises very severely all attempts to carry the Darwinian principle of explaining adaptations into internal and minute details, arguing against Roux’s “Struggle of Parts” and Weismann’s “Germinal Selection.” And though he himself maintains very decidedly that the ultimate aim of biology is to find a mechanical solution of the problem of life, he criticises the modern hypotheses in this direction without prejudice, and declares them unsuccessful and insufficient, inclining himself towards the “neo-vitalistic reaction” in its most recent expression.
To this category belong Darwin’s gemmules, Haeckel’s plastidules, Nägeli’s micellæ, Weismann’s labyrinth of ids, determinants, and biophors within the germ-plasm, and Roux’s ingenious hypothesis of the struggle of parts, which is an attempt to apply the Darwinian principle within the organism in order here also to rebut the teleological interpretation by giving a scientific one. Heredity.
A specially energetic fellow-worker on Eimer’s line is W. Haacke, a zoologist of Jena, author of “Gestaltung und Vererbung,” and “Die Schöpfung des Menschen und seiner Ideale.” In the first of these works Haacke combats, energetically and with much detail, Weismann’s “preformation theory,” and defends “epigenesis,” for which he endeavours to construct graphic diagrams, his aim being to make a foundation for the inheritance of acquired characters, definitely directed evolution, saltatory, symmetrical, and correlated variation.
What is there, for instance, in Weismann’s ingenious biophor-theory that can be called specifically biological, and not borrowed from other parts of the scientific system?
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