Wolff observed in great detail the early processes of embryonic differentiation. He disposed of the “preformation” theory, substituting his view that the organs are formed from leaf-like (blastodermic) layers. He thus laid the foundation of the “germ-layer” theory of Baer and Pander. His book includes descriptions of the “Wolffian bodies” and “ducts”. Reprinted 1966.

One of the acknowledged classics of embryology. Wolff’s description of the formation of the chick’s intestine by the rolling inwards of a leaf-like layer of the blastoderm was important as proving his theory of epigenesis. A German translation by J. F. Meckel was published in 1812.