INTRODUCTION. 

 1? 



11 



JtFS- 



Al 



\ -~ 



A 



B 







FIG. 9, A, B, AND C. DIAGRAMS ILLUSTRATING THE FORMATION OF THE AMNION, 

 ALLANTOIS, AND YOLK-SAC. A AND B, IN LONGITUDINAL SECTION ; C, IN 

 TRANSVERSE SECTION. 



E, embryo ; Dh, alimentary tract ; Do, yolk-sac ; t, vitello-intestinal duct ; PP, 

 body-cavity; Ah, amniotic cavity; AF, amniotic fold; A, amnion ; Al, 

 allantois ; a, somatopleure ; b, splanchnopleure ; AT, medullary cord ; C, notochord. 



