. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. Fig. 134. — Two nuclear spindles from the yolk of the germinal disc of a Trout's egg: the centrosome is exerting a disturbing influence upon the arrangement and distribution of the daughter-segments of the second spindle. (After Hennegu\.) the same category. It is well known, that a large number of nuclei (merocytes) are scattered throughout the yolk layer; this is situated below the germinating cells in eggs, which are partially segmented by furrows. Occasionally some of them collec
. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. Fig. 134. — Two nuclear spindles from the yolk of the germinal disc of a Trout's egg: the centrosome is exerting a disturbing influence upon the arrangement and distribution of the daughter-segments of the second spindle. (After Hennegu\.) the same category. It is well known, that a large number of nuclei (merocytes) are scattered throughout the yolk layer; this is situated below the germinating cells in eggs, which are partially segmented by furrows. Occasionally some of them collect to- gether to form small spindle aggregations, whilst at the same time they are making preparations for division. Hence it is very instructive to see, that in the following case, de- scribed by Henneguy (Fig. 134), the centrosomes act as attraction centres. Two me- rocytes, which are in the act of dividing, lie close together in the common mass of yolk, so that the longitudinal axis of spindle B would, if pro- duced, cut spindle A in its equator ; we see also that the one centrosome h is very near to spindle A. In con- sequence, the arrangement of the daughter-segments of spindle A has been, disturbed to a considerable extent. Instead of their being arranged in two groups near the centrosomes, a, a, as would occur normally, a number of those which are within the attraction sphere of the centrosome h of the neighbouring foreign spindle have been drawn towards it. In a word : the centrosome of the one spindle has evidently exerted a disturbing influence upon the arrangement and distribution of the daughter-segments of the other spindle. Henneguy has observed triasters, such as the one depicted in Fig. 135, and also tetrasters, in the germinal cells of the same object; these gradually separated themselves from the layer of merocytes. At the close of this fourth section we may mention the degeneration processes, which sometimes occur in cell nuclei, apparently as the result of
Size: 1504px × 1662px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectanatomy, booksubjectphysiology, booky
