. Cytology, with special reference to the metazoan nucleus. Cells; Cytology. THE ACHROMATIC FIGURE 21 ::i. ,.^ 'i however, that they only form a special case of karyosomes present in varying numbers, and often not traceable into the prophase chromosomes. (5) The Achromatic Figure This is the name given to the centrosome and system of radiating lines proceeding from it through the cytoplasm, which are plainly con- cerned with the separation of the daughter chromosomes. The term refers to the fact that (with the exception of the centrosome and centriole) the substance of which the system is comp
. Cytology, with special reference to the metazoan nucleus. Cells; Cytology. THE ACHROMATIC FIGURE 21 ::i. ,.^ 'i however, that they only form a special case of karyosomes present in varying numbers, and often not traceable into the prophase chromosomes. (5) The Achromatic Figure This is the name given to the centrosome and system of radiating lines proceeding from it through the cytoplasm, which are plainly con- cerned with the separation of the daughter chromosomes. The term refers to the fact that (with the exception of the centrosome and centriole) the substance of which the system is composed (sometimes known as the archoplasm) has much the same weak staining reaction as the bulk of the cytoplasm and the linin. The main features of its development during mitosis and its general disposition have already been described (Fig. 2). A complete achromatic figure at the metaphase of mitosis consists of the following parts : (i) A minute deeply staining centrosome occupies the centre of the radia- tions at each pole of the figure, and may contain (2) a still smaller central granule, the centriole. The centrosome is the point of insertion ^ of the so-called fibres of the achromatic figure, namely, (3) the radiating fibres composing i\\e aster, and the spindle fibres. The latter are of two kinds, (4) the mantle fibres, which are attached to the chromosomes, and (5) the fibres of the central spindle, which run right through from one centrosome to the other. In many forms, however, a central spindle seems to be absent. The terminology of these various parts is unfortunately in some confusion, especially so far as concerns the centrosome and immediately associated structures. This is largely because the centres of the system are occupied by a substance arranged in concentric layers, and opinions differ as to how much of this should be called centrosome. The centriole is very often, indeed generally, indistinguishable from the rest of the centrosome, and in this book the latt
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcells, bookyear1920
