VI CONTENTS. 



PAon 



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 EAKLIER HISTORY OF ONTOGENY. 



Caspar Frtedrich Wolff. 



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

 the Ontogeny of the. Lower Animals. — Stationary Condition of the 



cientific 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- 

 ighi. — 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. — Ovnlists : Haller, Leib- 

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



uthority of Haller and Leibnitz. — Caspar Friedrich Wolff. — His 

 Fate and Works. — Tne Theoria Generationis. — Re-formation, or 

 Epigenesis. — Tbe History of the Evolution of the Intestinal Canal. 

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

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

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



CHAPTER III. 



MODERN ONTOGENY. 



Karl Ernst Baer. 



Karl Ernst Baer, the Principal Disciple of Wolff. — The Wxirzburg 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 ai'ises 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- 



