CHAPTER XIV

THE PRINCIPLES OF EMBRYOLOGY

The law of recapitulation--Vindication of this law by the theory advanced in this book--The germ-layer theory--Its present position-- A physiological not a morphological conception--New fundamental law required--Composition of adult body--Neuro-epithelial syncytium and free-living cells--Meaning of the blastula--Derivation of the Metazoa from the Protozoa--Importance of the central nervous system for Ontogeny as well as for Phylogeny--Derivation of free-living cells from germ-cells--Meaning of coelom--Formation of neural canal--Gastrula of Amphioxus and of Lucifer--Summary 455