CONTENTS IX 



CHAPTER XIII 



PAGE 



THE DEVELOPMENT OF THE CHICK DURING THE THIRD AND FOURTH DAYS 



OF INCUBATION 109 



I. External Features. 



Torsion; flexion; the visceral arches and clefts; the oral region; 

 the appendage buds; the allantois. 

 II. The Nervous System. 



Summary of development prior to the third day; the formation 

 of the telencephalic vesicles; the diencephalon; the mesen- 

 cephalon; the metencephalon; the myelencephalon; the ganglia 

 of the cranial nerves; the spinal cord; the spinal nerve roots. 



III. The Sense Organs. 



The eye; the ear; the olfactory organs. 



IV. The Digestive and Respiratory Systems. 



Summary of development prior to the third day; the establish- 

 ment of the oral opening; the pharyngeal derivatives; the 

 trachea; the lung-buds; the oesophagus and stomach; the 

 liver; the pancreas; the mid-gut region; the cloaca; the procto- 

 daeum and the cloacal membrane. 

 V. The Circulatory System. 



The functional significance of the embryonic circulation; the 

 vitelline circulation; the allantoic circulation; the intra-embry- 

 onic circulation; the heart. 

 VI. The Urinary System. 



The general relationships of pronephros, mesonephros, and 

 metanephros; the pronephric tubules of the chick; the meso- 

 nephric tubules. 



VII. The Ccelom and Mesenteries. 



APPENDIX 



REFERENCES FOR COLLATERAL READING X 55 



INDEX T 6i 



