DEVELOPMENT PRIOR TO LAYING 49 
served that the large marginal cells on each side are continuous 
with the periblast, and nuclei are found in the periblast both 
central and peripheral to the zone of junction. The latter forms 
3 
a ater ae | 
es nn ees ae 
Fic. 21. — Longitudinal section of the blastoderm of a pigeon’s egg at the 
time of disappearance of the sperm-nuclei. On the left (anterior) margin, 
the marginal cells have become open, that is, continuous with the peri- 
blast, as contrasted with Fig. 20. About 11 hours after fertilization (7.00 
A.M.). (After Blount.) 
1, Marginal cells. 2, Cone of protoplasm. 3, Marginal periblast. 4, Neck 
of latebra. 5, Yellow yolk. 
Fic. 22. — Transverse section through the center of the blastoderm of a 
pigeon’s egg, 144 hours after fertilization (10.30 a.m.). (After Blount.) 
1, Marginal cells. 2, Marginal periblast. 3, Nuclei of the subgerminal 
periblast. 
