. Analysis of development. Embryology; Embryology. V Cellular Structure and Activity -IP'*' <'Tft ^i \ ^ m mn Fig. 10. Mitosis in the whitefish blastula (from Turtox slides) seem to fall outside of the general picture (but cf. DeLamater and Mudd, '51). The divisions of the blastomeres in the whitefish blastula are useful to describe the morphological aspects of mitosis in an ani- mal cell (Fig. 10). Following Strasburger the process is subdivided into four phases: During prophase the centrosome divides (Fig. 10^); the centrioles are not visible in these preparations but can be demonstrated
. Analysis of development. Embryology; Embryology. V Cellular Structure and Activity -IP'*' <'Tft ^i \ ^ m mn Fig. 10. Mitosis in the whitefish blastula (from Turtox slides) seem to fall outside of the general picture (but cf. DeLamater and Mudd, '51). The divisions of the blastomeres in the whitefish blastula are useful to describe the morphological aspects of mitosis in an ani- mal cell (Fig. 10). Following Strasburger the process is subdivided into four phases: During prophase the centrosome divides (Fig. 10^); the centrioles are not visible in these preparations but can be demonstrated in slides stained with iron-hematoxylin (Fig. 11). The chromosomes now appear embedded in eosin- ophilic material that later forms the spindle (Figs. lOA and B) and finally the nuclear membrane breaks down (Fig. IOC). While the spindle takes shape the chromosomes be- come oriented in the equatorial plane (Fig. 107)): metaphase. During anaphase the chromosomes move toward the spindle poles and the spindle elongates (Figs. lOE, F, G). Finally, in telophase the nuclear membrane reappears, in this case around each chomo- some separately, so that karyomeres are formed which later may fuse into a single nucleus. The cytoplasm is subdivided by the cleavage furrow (Fig. lOH). This account of mitosis in the whitefish blastomere has been pieced together from various stages in fixed and stained cells. Is it possible to follow the process in the living cell as it divides? If we place the blastula of a whitefish egg during cleavage in calcium- free Ringer's solution and gently squeeze it in a rotocompressor,* the cells separate and a single layer of cells can be obtained. For some time the blastomeres continvie to divide Fig. 11. Prophase in blastomere of whitefish, stained with iron-hematoxylin to show centriole. phi * Obtained from Biological Institute, Philadel-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - c
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Keywords: ., bookcentury1900, bookpublisherphiladelphi, booksubjectembryology
