yj CONTENTS. 



PACK 



Morphogeny. The History of Evolution as yet almost entirely 

 the Product of Morphology, and not of Physiology. The History 

 of the Evolution of the Central Nervous System (Brain and Spinal 

 Marrow) is involved in that of the Psychic Activities, or the Mind 1 



CHAPTER II. 



THE EARLIER HISTORY OF ONTOGENY. 

 CASPAR FRIEDRICH WOLFF. 



The Evolution of Animals as known to Aristotle. His Knowledge of 

 the Ontogeny of the Lower Animals. Stationary Condition of the 

 Scientific Study of Nature during the Christian Middle Ages 

 First Awakening of Ontogeny in the Beginning of the Seventeenth 

 Century. Fabricius ab Aquapendente. Harvey. Marcello Mal- 

 pighi. Importance of the Incubated Chick. The Theories of Pre- 

 formation and Encasement (Evolution and Pre-delineation). 

 Theories of !Male and Female Encasement. Either the Sperm- 

 animal or the Egg as the Pre-formed Individual. Animalculists : 

 Leeuwenhoek, Hartsoeker, Spallanzani. Ovulists : Haller, Leib- 

 nitz, Bonnet. Victory of the Theory of Evolution owing to the 

 Authority of Haller and Leibnitz. Caspar Friedrich Wolff. His 

 Fate and Works. The Theoria Generationis. Re-formation, or 

 Epigenesis. The History of the Evolution of the Intestinal Canal. 

 The Foundations of the Theory of Germ-layers (Four Layers, 

 or Leaves). The Metamorphosis of Plants. The Germs of the 

 Cellular Theory. Wolff's Monistic Philosophy... ... ... 25 



CHAPTER III. 



MODERN ONTOGENY. 

 KARL EKNST BAER. 



Karl Ernst Baer, the Principal Disciple of Wolff. The Wurzburg School 

 of Embryologists : Dollinger, Pander, Baer. Pander's Theory of 

 Germ-layers. Its Full Development by Baer. The Disc-shaped 

 first parts into Two Germ-layers, each of which again divides into 

 Two Strata. The Skin or Flesh-stratum arises from the Outer or 

 Animal Germ-layer. The Vascular or Mucous Stratum arises from 

 the Inner or Vegetative Germ-layer. The Significance of the 

 Germ-layers. The Modification of the Layers into Tubes. Baer's 

 Discovery of the Human Egg, the Germ-vesicle, and Chorda Dor- 



