X CONTENTS. 



CHAPTER XXII. 



DEVELOPMENT OP THE ORGANS OF MOTION. 



FAtil 



The Motive Apparatus of Vertebrates. — These are constituted by the 

 Passive and Active Organs of Motion (Skeleton and Musoles). — 

 The Significance of the Internal Skeleton of Vertebrates. — Struc- 

 ture of the Vertebral Column. — Formation and Number of the 

 Vertebrae. — The Ribs and Breast-bone. — Germ-history of the Verte- 

 bral Column. — The Notochord. — The Primitive Vertebral Plates. — 

 The Formation of the Metamera. — Cartilaginous and Bony Verte- 

 brae. — Intervertebral Discs. — Head-skeleton (Skull and Gill-arches). 

 — Vertebral Theory of the Skull (Goethe and Oken, Huxley and 

 Gegenbaur). — Primitive Skull, or Primordial Cranium. — Its Forma- 

 tion from Nine or Ten Coalescent Metamera. — The Gill-arches 

 (Ribs of the Head). — Bones of the Two Pairs of Limbs. — Develop- 

 ment of the Five-toed Foot, adapted for Walking, from the Many- 

 toed Fin of the Fish. — The Primitive Fin of the Selachians 

 (Archipterygium of Gegenbaur). — Transition of the Pinnate into 

 the Semi-pinnate Fin. — Atrophy of the Rays or Toes of the Fins. — 

 Many-fingered and Five-fingered Vertebrates.— Comparison of the 

 Anterior Limbs (Pectoral Fins) and the Posterior Limbs (Ventral 

 Fins). — Shoulder Girdle and Pelvis Girdle. — Germ-history of the 

 Limbs. — Development of the Muscles ... ... ... 273 



CHAPTER XXIII. 



DEVELOPMENT OF THE INTESTINAL SYSTEM. 



The Primitive Intestine of the Gastrula. — Its Homology, or Morpho- 

 logical Identity in all Animals (excepting the Protozoa). — Survey 

 of the Structure of the Developed Intestinal Canal in Man. — The 

 Mouth-cavity. — The Throat (pharynx). — The Gullet (oesophagus). — 

 The Wind-pipe (trachea) and Lungs. — The Larynx. — The Stomach. 

 — The Small Intestine. — The Liver and Gall-bladder. — The Ventral 

 Salivary Gland (pancreas). — The Large Intestine. — The Rectum. — 

 The First Rudiment of the Simple Intestinal Tube. — The Gastrula 

 of the Amphioxus and of Mammals. — Separation of the Germ from 

 the Intestinal Germ Vesicle (Gastrocystis). — The Primitive Intes- 

 tine (Protogaster) and the After Intestine (Metagaster) . — Secondary 

 Formation of the Mouth and Anus from the Outer Skin. — Develop- 

 ment of the Intestinal Epithelium from the Intestinal-glandular 

 Layer, and of all other parts of the Intestine from the Intestinal- 

 fibrous Layer. — Simple Intestinal Pouch of the Lower Worms.— 



