Zeit- und Straitfragen der Biologie

Abstract

THE theory of preformation, or rather let us say predetermination, as revived at the close of the nineteenth century, is much more formidable than its prototype of the eighteenth century. Not only is it stripped of all its earlier crudities, such as the doctrine of êmboitement, but it is supported by a mass of evidence accumulated by the researches of the last quarter of a century. Its fundamental assumption, that of the existence of minute, qualitatively unlike, ultimate particles of living matter, is strengthened, if not supported, by the analogy of the atomic theory, and the observed phenomena of mitosis accompanying the maturation of the ovum and spermatozoon, and the subsequent acts of impregnation and segmentation have been skilfully blended with the fundamental assumption in such a way that they are made to seem to be a proof of it. This strong position is now assailed by Dr. Oscar Hertwig, who is in many respects peculiarly well fitted to the task. He is the master of a simple, lucid and logical style, he has himself been, in conjunction with his brother, a pioneer in many of the discoveries on which the doctrine of predetermination is founded, and he has recently set himself to the task of verifying the experiments of Roux and others, and of examining the evidence which they afford for or against the doctrine which he attacks. His answer is unequivocal. The phenomena of development are to be explained on epigenetic, not on evolutionary grounds, and the latter hypothesis is contradicted by a number of well-ascertained facts. Zeit- und Straitfragen der Biologie. Von Prof. Dr. Oscar Hertwig. Heft 1: Präformation oder Epigenese? Grundzüge einer Entwicklungs-theorie der Organismen. (Jena: Gustav Fischer, 1894.)