. The cell in development and inheritance. Cells. DETAILS OF MITOSIS S7 of the spindle as usual. As will be shown in Chapter V.,the divisions by which the germ-cells are matured are in many cases of this type; but the primary rings here in many cases represent not two but four chromosomes, into which they afterward break Fig. 37.— Heterotypical mitosis in spermatocytes of the salamander. [Flemming.] A. Prophase, chromosomes in the form of scattered rings, eacli of which represents two daughter-chromosomes joined end to end. B. The rings ranged about the equator of the spindle and dividing
. The cell in development and inheritance. Cells. DETAILS OF MITOSIS S7 of the spindle as usual. As will be shown in Chapter V.,the divisions by which the germ-cells are matured are in many cases of this type; but the primary rings here in many cases represent not two but four chromosomes, into which they afterward break Fig. 37.— Heterotypical mitosis in spermatocytes of the salamander. [Flemming.] A. Prophase, chromosomes in the form of scattered rings, eacli of which represents two daughter-chromosomes joined end to end. B. The rings ranged about the equator of the spindle and dividing ; the swellings indicate the ends of the chromosomes. C. The same viewed from the spindle-pole. D. Diagram (Hermann) showing the central spindle, asters, and the contractile mantle-fibres attached to the rings (one of the latter dividing). 2. Bivalciit and Plurivalcjit Chromosomes The last paragraph leads to the consideration of certain varia- tions in the number of the chromosomes. Boveri discovered that the species Ascaris vicgaloccpJiala comprises two varieties which differ in no visible respect save in the number of chromosomes, the germ-nuclei of one form (" variety bivalens " of Hertwig) having two chromosomes,. 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 Wilson, Edmund B. (Edmund Beecher), 1856-1939. New York Macmillan
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1906
