. Cytology, with special reference to the metazoan nucleus. Cells. ^\ Y !. •••• H ' I V Fig. 49. I The chromosomes of Syromastes (A, B) and Acholla multispinosa (C-I). (Wilson, , 1909 a, and Payne, fi.^.,1910.) In A and B the X chromosomes are blackened. A, (5 diploid group, 20 fXo = 22 chromosomes; B, ? diploid group, 20 + 2X2 = 24 chromosomes : C, 9 diploid group, 20+2X^ = 30 chromosomes. The three pairs of small X elements are easily seen, the other two pairs are not at this stage distinguishable. D, i diploid group 2o4-X5+Y = 26 chromosomes; E, metaphase l.,i, polar view. The Y element
. Cytology, with special reference to the metazoan nucleus. Cells. ^\ Y !. •••• H ' I V Fig. 49. I The chromosomes of Syromastes (A, B) and Acholla multispinosa (C-I). (Wilson, , 1909 a, and Payne, fi.^.,1910.) In A and B the X chromosomes are blackened. A, (5 diploid group, 20 fXo = 22 chromosomes; B, ? diploid group, 20 + 2X2 = 24 chromosomes : C, 9 diploid group, 20+2X^ = 30 chromosomes. The three pairs of small X elements are easily seen, the other two pairs are not at this stage distinguishable. D, i diploid group 2o4-X5+Y = 26 chromosomes; E, metaphase l.,i, polar view. The Y element is characteristically in association with the two largest of the X elements. F, G, anaphase I., side view cut in two section?. The section in F contains the Y and the two large X elements, and that in G the three small X elements. H, I, anaphase II., showing the results of the segregating division. following examples illustrate the range of variation in the constitution of the sex chromosome (Fig. 51) : (A) No Y chromosome present. X Chromosome single {Prolenor). double (Syromastes). I. 2. X 3. X pentad [Ascaris lumbricoides). (B) Simple Y chromosome present. 1. X Chromosome single [Lygaeiis, Oncopeltus), 2. X ,, double [Fitchia). 3. X „ triple [Prionidus). 4. X ,, quadruple {Gelastocoris). 5. X . „ pentad [Acholla tnnlUspmosa).. 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, Wilfred Eade, 1882-. London, Macmillan
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcells, bookyear1920
