. The physical basis of heredity . letely than any other, andit serves also to illustrate clearly the relationship of thechromosomes to the vesicles into which they pass (orwhich they form) during the resting stages. The figuresalso show how the threads emerge from the vesicles inwhich they appear to have been contained during theresting stages, and how the opening out of the tetradsin two planes gives the appearance of chiasma accord-ing to Wenrich. During the time when the germ-cells are increasing innumber by division there is a restiitg stage after each CROSSING OVER AND CHROMOSOMES 105 di
. The physical basis of heredity . letely than any other, andit serves also to illustrate clearly the relationship of thechromosomes to the vesicles into which they pass (orwhich they form) during the resting stages. The figuresalso show how the threads emerge from the vesicles inwhich they appear to have been contained during theresting stages, and how the opening out of the tetradsin two planes gives the appearance of chiasma accord-ing to Wenrich. During the time when the germ-cells are increasing innumber by division there is a restiitg stage after each CROSSING OVER AND CHROMOSOMES 105 division during which the chromosomes expand into asort of vesicle, as seen by comparing Figs. 44, a and44, h. An optical cross section of the stages shownin the last figure is represented in Fig. 44, c. Anolder stage is seen in Fig. 44, d. The stage of greatestdiffusion of the chromatin material within its vesicle isseen in this figure, where the outlines of each vesicle arestill visible. As the nucleus gets ready for another divi-.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectheredit, bookyear1919
