. The cell in development and inheritance. Cells. ORIGIN OF THE TETRADS 189 pods by Riickert, Hacker, and vom Rath, in the frog by vom Rath, and in elasmobranchs by Moore. The genesis of the ring was first determined by vom Rath in the mole-cricket {Gryllotalpa, '92), and has been thoroughly elucidated by the later work of Riickert ('94) and Hacker ('95, i). All these observers, excepting Wilcox and. °00§ 0\\ • •; ... , . Cl_ OOOO 0 0 1)0 ^O 0 ° ° o ^J^^ D Fig. 94. — Formation of the tetrads and polar bodies in Cyclops, slightly schematic. (The full number of tetrads is not shown.) [RiicKERT.]
. The cell in development and inheritance. Cells. ORIGIN OF THE TETRADS 189 pods by Riickert, Hacker, and vom Rath, in the frog by vom Rath, and in elasmobranchs by Moore. The genesis of the ring was first determined by vom Rath in the mole-cricket {Gryllotalpa, '92), and has been thoroughly elucidated by the later work of Riickert ('94) and Hacker ('95, i). All these observers, excepting Wilcox and. °00§ 0\\ • •; ... , . Cl_ OOOO 0 0 1)0 ^O 0 ° ° o ^J^^ D Fig. 94. — Formation of the tetrads and polar bodies in Cyclops, slightly schematic. (The full number of tetrads is not shown.) [RiicKERT.] A. Germinal vesicle containing eight longitudinally split chroniatin-rods (half the somatic number). D. Shortening of the rods; transverse division (to form the tetrads) in progress. C. Position of the in the first polar spindle, tlie longitudinal split horizontal. D. Ana- phase ; longitudinal division of the tetrads. E. The first polar body formed; second polar spindle with the eight dyads in position for the ensuing division, which will be a transvetse or reducing division. Moore (see p. 201), have reached the same conclusion; namely, that the ring arises by the longitudinal splitting of a primary chromatin- rod, the two halves remaining united by their ends, and opening out to form a ring. The ring-formation is, in fact, a form of heterotypi- cal mitosis (p. 60). The breaking of the ring into four parts involves. 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 : The Macmillan company
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectcells, bookyear1896
