. The cell in development and inheritance. Cells. Fig. 165.— Kggs of Ascaris with supernumerary centrosome. [BOVERI.] A. First cleavage-spindle above, isolated centrosome below. B. Result of the ensuing division. into connection with the chromosomes, but lies alone in the cytoplasm (Fig. 165). Such a centrosome forms an independent centre of divi- sion, the cell dividing into three parts, two of which are normal blastomeres, while the third contains only the centrosome and attrac- tion-sphere. The fate of such eggs was not determined, but they form a complete demonstration that it is in this c
. The cell in development and inheritance. Cells. Fig. 165.— Kggs of Ascaris with supernumerary centrosome. [BOVERI.] A. First cleavage-spindle above, isolated centrosome below. B. Result of the ensuing division. into connection with the chromosomes, but lies alone in the cytoplasm (Fig. 165). Such a centrosome forms an independent centre of divi- sion, the cell dividing into three parts, two of which are normal blastomeres, while the third contains only the centrosome and attrac- tion-sphere. The fate of such eggs was not determined, but they form a complete demonstration that it is in this case the centrosome and not the nucleus that determines the centres of division in the cell-body. Scarcely less conclusive is the case of dis^grmic eggs in sea-urchins. In such eggs both sperm-nuclei conjugate with the egg- nucleus, and both sperm-centrosomes divide (Fig. 166). The cleavage-nucleus, therefore, arises by the union of tJiree nuclei and foiir centrosomes. Such eggs divide at the first cleavage into four equal blastomeres, each of which receives one of the centrosomes. 1 Cf. 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, bookdecade1910, booksubjectcells, bookyear1911
