. The cell in development and inheritance. Cells. B C Fig. 137. — Types of maturation-spindles in the female. A. First polar spindle with tetrads, in Heterocope. [HaCKER]. B. Second polar spindle in Triton. [ and LeBrun.] C. First polar spindle of .;7r/j-. [FURST.] vesicle at the time the polar bodies are formed (Figs. 97, 128). In these cases (Asterias, Polyeho^rus, Thalassenia, Nereis) only a small fraction of the chromatin-substance is preserved to form the chromo- somes, the remainder degenerating in the As a final point we must briefly consider the varying accoun
. The cell in development and inheritance. Cells. B C Fig. 137. — Types of maturation-spindles in the female. A. First polar spindle with tetrads, in Heterocope. [HaCKER]. B. Second polar spindle in Triton. [ and LeBrun.] C. First polar spindle of .;7r/j-. [FURST.] vesicle at the time the polar bodies are formed (Figs. 97, 128). In these cases (Asterias, Polyeho^rus, Thalassenia, Nereis) only a small fraction of the chromatin-substance is preserved to form the chromo- somes, the remainder degenerating in the As a final point we must briefly consider the varying accounts of the achromatic maturation-figures in the female already briefly referred to at page 85. In many forms { in turbellarians, nemertines, anne- lids, mollusks, echinoderms) the polar amj^hiasters are of quite typical form, with large asters and distinct centrosomes nearly similar to those of the cleavage-figures. In others, however (nematodes, arthropods, tunicates, vertebrates), the polar spindles differ markedly from those of the cleavage-figures, being described by many authors as entirely devoid of asters and even in some cases of centrosomes (Fig. 137). 1 Cf. Mathews (Wilson and Mathews, '95), Gardiner ('98), Griffin ('99). 2 Cf. the enormous reduction of the chromatin-substance in the elasmobraich egg, p. 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
