. The development of the chick; an introduction to embryology. Birds -- Embryology. DEVELOPMENT PRIOR TO LAYING 33 grating wail (Fig. 9). Tlie cliromosomes and nucleoli form a group near the center of the upper plane surface of the germinal Chr •>?^ f<^ -tf^ ^. Fig. 9. — Vertical section of the germinal vesicle and part of the germinal disc of an ovarian ovum | inch in diameter; pigeon, x 385. (After Harper.) Chr., Chromosomes. Gr., Granulosa. G. V., Wall of germinal vesicle. vesicle. The first maturation spindle is formed before ovulation, containing eight quadruple chromosomes (tetrads
. The development of the chick; an introduction to embryology. Birds -- Embryology. DEVELOPMENT PRIOR TO LAYING 33 grating wail (Fig. 9). Tlie cliromosomes and nucleoli form a group near the center of the upper plane surface of the germinal Chr •>?^ f<^ -tf^ ^. Fig. 9. — Vertical section of the germinal vesicle and part of the germinal disc of an ovarian ovum | inch in diameter; pigeon, x 385. (After Harper.) Chr., Chromosomes. Gr., Granulosa. G. V., Wall of germinal vesicle. vesicle. The first maturation spindle is formed before ovulation, containing eight quadruple chromosomes (tetrads). The spindle is still in the equatorial plate stage when the ovum is grasped by the mouth of the oviduct (Fig. 10). The bulk of the substance of the ger- minal vesicle soon forms a yolk-free cone extending from the maturation spin- dle deep into the superficial ^ ^ yolk. The outer end of the Fig. 10. — Vertical section of the germinal spindle is in almost imme- fh^c of the pigeon's egg showing the diate contact with the sur- ^^^^ maturation spindle. The egg was . clasped by the funnel or the oviduct, face of the ovum. In the g ^^ ^ ^^ ^ 2OOO. (After Harper.) later stages of formation of 1, First maturation spindle. Tetr., the first polar body each Tetrad. tetrad, or quadruple chromosome, separates into two dyads or double chromosomes, and the members of each pair of dyads separate and approach opposite ends of the spindle (anaphase).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattray, 1870-1947. New York, Holt
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