WILLIAM A. HILTON. 



10. In later >tages of gastrulation there is a marked ingrowth 

 from the dm>al lip of the blastopon 



11. Dorsal and ventral mesoblast become fused in later stages 

 due to the ("in-mat it in of the caudal mass in front of and about 

 the blastopore. 



12. The caudal mass furnishes mesoblast in all directions. 

 That funned raudally and laterally grows between the yolk cells 

 and ectoblast. Later, the growing edges of the mesoblast fuse 

 to enclose practically the whole yolk mass. 



CORNELL UNIVERSITY, 



DEPARTMENT OF HISTOLOGY AND EMBRYOLOGY. 



