* CONTENTS. 



CHAPTER XXII. 



DEVELOPMENT OF THE ORGANS OF MOTION. 



PAOB 



The Motive Apparatus of Vertebrates. These are constituted by tho 

 Passive and Active Organs of Motion (Skeleton and Mu?>les). 

 The Significance of the Internal Skeleton of Vertebrates. Struc- 

 ture of the Vertebral Column. Formation and Number of the 

 Vertebrao. 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 

 (ArcMpterygium of Gegeubaur). 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 (Pectoi-al 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. 



