The Non-Specificity of the Germ-Layers

Abstract

This is a historical and critical review of the doctrine of the specificity of the germ-layers in embryology. It. describes briefly its establishment based on the work of Pander, von Baer and Remak, and its further elaboration in connection with the evolution-theory by Huxley, Ko-walewski, Haeckel, the Hertwigs and others. The criticisms of the doctrine made in the last century are collected and evidence is cited from modern exptl. embryology showing that the accomplishments of individual layers may be far less specific than was suggested by the early investigators who established the familiar dogmatized concept.