CONTENTS vii 



PAGE 



The Turning of the Embryo and the Embryonic Flexures 133 



II. ORIGIN OF THE EMBRYONIC MEMBRANES 135 



Origin of the Amnion and Chorion 135 



The Yolk-sac 143 



Origin of the Allantois . . . . . 143 



Summary of Later History of the Embryonic Membranes . 145 



III. THE NERVOUS SYSTEM . . . . . 147 



The Brain 147 



The Neural Crest and the Cranial and Spinal Ganglia 156 



IV. THE ORGANS OF SPECIAL SENSE (EYE, EAR, NOSE) . 164 



The Eye . . 164 



The Auditory Sac 168 



The Nose (Olfactory Pits) 169 



V. THE ALIMENTARY CANAL AND ITS APPENDAGES . . . 170 



The StomodcBum 173 



The Pharynx and Visceral Arches 173 



(Esophagus and Stomach 179 



The Liver .179 



The Pancreas 181 



The Mid-Gut 181 



Anal Plate, Hind-gut, Post-anal gut and Allantois 182 



VI. HISTORY OF THE MESODERM 183 



Somites 183 



The Intermediate Cell-mass 190 



The Vascular System .197 



VII. THE BODY-CAVITY AND MESENTERIES 205 



PART II 



THE FOURTH DAY TO HATCHING, ORGANOGENY, 

 DEVELOPMENT OF THE ORGANS 



CHAPTER VII. THE EXTERNAL FORM OF THE EM- 

 BRYO AND THE EMBRYONIC MEMBRANES 211 



I. THE EXTERNAL FORM . .211 



General .211 



Head 213 



II. EMBRYONIC MEMBRANES 216 



General 216 



The Allantois 220 



The Yolk-sac . 225 



The Amnion 231 



Hatching 232 



