. The cell in development and inheritance. Cells. 320 SOME PROBLEMS OF The amphiastral formation in alveolar protoplasm ^ivcs very clear evidence against the theory of fibrillar persistence. Here the fibrillar rays can be seen i;ro\ving- out throui;h the walls of the alveoli^ quite distinct from, though embedded in, them. At the close of mitosis every trace of the fibrillar formation may disappear, in echino- derm-eggs after formation of the polar bodies, the protoplasm retain- ing only a typical alveolar structure. i. Fig. 155. — Stages in the first cleavage of the e
. The cell in development and inheritance. Cells. 320 SOME PROBLEMS OF The amphiastral formation in alveolar protoplasm ^ivcs very clear evidence against the theory of fibrillar persistence. Here the fibrillar rays can be seen i;ro\ving- out throui;h the walls of the alveoli^ quite distinct from, though embedded in, them. At the close of mitosis every trace of the fibrillar formation may disappear, in echino- derm-eggs after formation of the polar bodies, the protoplasm retain- ing only a typical alveolar structure. i. Fig. 155. — Stages in the first cleavage of the egg in Cerebratnlits (A-C, COE) and Thalasseyna {D-F, Griffin). A. First appearance of the cleavage-centrosome at the poles of the fused germ-nuclei; cleavage- asters forming within the degenerating sperm-asters. B. Final anaphase of first cleavage, showing persistent centrosomes and new asters forming. C. Immediately after division. D-F. Three stages of the late anaphase in Thalasseyna, showing formation of new asters within the old. {Cf. Fig. 99.) The strongest evidence against fibrillar persistence is, however, given by recent studies on mitosis, showing on the one hand that the new astral centres do not coincide with the old ones, on the other that the old rays degenerate /// situ, to be replaced by new ones. Aside from many earlier observers, who believed the entire aster to disappear at the close of mitosis, the first to assert the wholly new 1 Cf. Reinke ('95), Wilson ('99).. 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
