SEGMENTATION OF THE EGG. 



21 



Fig. 4.— The Hen's Egg, freshly laid, x ;;. 

 BA, germinal rlisc. SH, egg shell. SM, shell membraQC. SV, air chamber. 

 W A, white or albumen, "WO, chalaza. Y yolk. Z, vitelline membrane. 



Fig. 5. Fig. 6, 



Figs, 5, 6, — Stages in the segmentation of the germinal disc of the 



Hen's Egg, x 10, (After Ooste and Duval.) 



B ZL 



Pig. 7. — Vertical section of the germinal disc of the Hen's Egg at 

 the close of segmentation; x 25. (After Duval.) 

 B, segmentation cavity or blastoccEl. E, upper layer of blastomeres, or epiblast. 

 N"', nucleus of incompletely formed blastomere, VJJj vacuole in yolk. Y, yolk 

 ZL, lower layer of blastomeres. 



