. Cunningham's Text-book of anatomy. Anatomy. Fig. 15.âSchema of Maturation of Oycm in Metaphasb of First Division. One pole of the spindle projects into the first polar bud, and the maternal and paternal parts of the chromosomes are separating from each other. Oolemma Polar bud with chro- Achromatic _ ^ ,, spindle ,â '"*>"-'^ <^V lies in the region of the larger deutoplasmic granules by which its presence is frequently obscured. The Mitochondria.âThese minute particles can be demonstrated by suitable methods of fixation and staining. The Maturation of the Ovum.âThe p
. Cunningham's Text-book of anatomy. Anatomy. Fig. 15.âSchema of Maturation of Oycm in Metaphasb of First Division. One pole of the spindle projects into the first polar bud, and the maternal and paternal parts of the chromosomes are separating from each other. Oolemma Polar bud with chro- Achromatic _ ^ ,, spindle ,â '"*>"-'^ <^V lies in the region of the larger deutoplasmic granules by which its presence is frequently obscured. The Mitochondria.âThese minute particles can be demonstrated by suitable methods of fixation and staining. The Maturation of the Ovum.âThe process of maturation consists of two mitotic divisions, of which the first is hetero- typical, and results in the reduction of the number of chromosomes, and the second is homotypical. The phenomena of the two divisions differ in some of their details from those of ordinary cell divisions, therefore a short account of them is necessary. In the prophase of the first maturation division, the centrosome, the nucleolus, and the nucleus vanish,and an achromatic spindle appears at one pole of the oocyte, where, it lies, at first, parallel with the surface; and the chromosomes are gathered around its equator. The number of the chromosomes is only half the typical number, and they are probably twin chromosomes (p. 11). There are no centrosomes at the poles of the spindle. After a short time the spindle rotates until it lies at right angles to its original position, and one pole, surrounded by a small amount of the cytoplasm, forms a projection, the first polar projection, on the surface of the oocyte (Fig. 14). During the metaphase the twin chromo- somes divide. In the anaphase the daughter chromosomes travel to the opposite poles of the spindle, and at the end of the anaphase one-half of the daughter chromosomes lies in the first polar projection and the other half in the body of the oocyte (Fig. 16). In the telophase the first polar projection Fig. 16.âSchema of Maturation is se
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
