Archive image from page 63 of The development of the chick;. The development of the chick; an introduction to embryology . developmentofchi00lill Year: 1908 46 THE DEVELOPMENT OF THE CHICK the accessory cleavage-cells and also in the unsegmented periblast (Figs. 19 and 20), they decrease in number as the accessory cleavage planes disappear, and when the latter are entirely lost 1 •> Fig. 19. — Transverse section of the blastoderm of a pigeon's egg about 8| hours after fertilization ( ). (After Blount.) 1, Accessory cleavage. 2, Migrating sperm-nuclei, a, b, c, d, Cells of primar
Archive image from page 63 of The development of the chick;. The development of the chick; an introduction to embryology . developmentofchi00lill Year: 1908 46 THE DEVELOPMENT OF THE CHICK the accessory cleavage-cells and also in the unsegmented periblast (Figs. 19 and 20), they decrease in number as the accessory cleavage planes disappear, and when the latter are entirely lost 1 •> Fig. 19. — Transverse section of the blastoderm of a pigeon's egg about 8| hours after fertilization ( ). (After Blount.) 1, Accessory cleavage. 2, Migrating sperm-nuclei, a, b, c, d, Cells of primary cleavage. the periblast is absolutely devoid of nuclei. Fragmentation of the sperm-nuclei is a frequent accompaniment of their disappearance. Thus the accessory cleavage is a secondary and transient feature of the cleavage of the pigeon's egg due to polyspermy. After it has passed, the ovum is in precisely the same condition
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