. Cytology, with special reference to the metazoan nucleus. Cells. 36 CYTOLOGY CHAP. pre-meiotic nuclei. As the chromosomes behave similarly in meiosis in the female, the fusion of the male and female gametes results in the reconstitution of a diploid nucleus with four chromosomes in two pairs. Thus, if we designate each of the differently shaded chromosomes of the diagram by a different letter, the gametes contain chromosomes. Fig. 15. Diagram of the principal stages of meiosis by parasyndesis. Two pairs of homologous chromosomes are shown, the members of one pair being stippled, and those of
. Cytology, with special reference to the metazoan nucleus. Cells. 36 CYTOLOGY CHAP. pre-meiotic nuclei. As the chromosomes behave similarly in meiosis in the female, the fusion of the male and female gametes results in the reconstitution of a diploid nucleus with four chromosomes in two pairs. Thus, if we designate each of the differently shaded chromosomes of the diagram by a different letter, the gametes contain chromosomes. Fig. 15. Diagram of the principal stages of meiosis by parasyndesis. Two pairs of homologous chromosomes are shown, the members of one pair being stippled, and those of the other cross-striped. A, pre-meiotic prophase, showing the four separate chromosomes ; B, leptotene ; C, pachytene ; D, diplotene stages ; E, diakinesis, showing the evolution of the definitive bivalents ; F, meiotic metaphase ; G, metaphase of second division of the meiotic phase in the secondary spermatocyte formed from the upper daughter nucleus derived from F. A + B, and the zygote A + A + B + B. In syndesis pairing takes place in such a way that the pachytene nuclei contain two bivalents, forming the series A A + BB. We also see that one member of each bivalent was originally introduced by the male gamete and the other by the female. While the most important features of meiosis are all to be found. 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 Agar, W. E. (Wilfred Eade), 1882-1951. London, Macmillan and Co. , limited
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcells, bookyear1920
