. Cytology, with special reference to the metazoan nucleus. Cells. ii MEIOSIS IN THE FEMALE 63 nature (amphinucleoli), consisting of a plastin groundwork (plasmosome), covered or impregnated with chromatin or a chromatin-like substance ; or the two constituents may be separate, so that the nucleolus consists of two parts, a chromatin and a plastin portion. These remarks refer especially to the main nucleolus, which persists right through the growth period. In many animals the secondary nucleoli which develop later. Fig. "26. Showing the fate of the nucleolus in the oogenesis of Daphnia pu
. Cytology, with special reference to the metazoan nucleus. Cells. ii MEIOSIS IN THE FEMALE 63 nature (amphinucleoli), consisting of a plastin groundwork (plasmosome), covered or impregnated with chromatin or a chromatin-like substance ; or the two constituents may be separate, so that the nucleolus consists of two parts, a chromatin and a plastin portion. These remarks refer especially to the main nucleolus, which persists right through the growth period. In many animals the secondary nucleoli which develop later. Fig. "26. Showing the fate of the nucleolus in the oogenesis of Daphnia pulex. (After Kuhn, , 1908.) A, the large central nucleolus is beginning to break up into much smaller bodies which are spreading over the thin threads representing the chromosomes ; B, C, the continuation of this process. In C the nucleolus has completely disintegrated into granules or droplets which conceal the chromosomes. D, the condensed chromosomes (c) embedded in the disintegrated nucleolar mass ; E, the meiotic division. Note the mass of nucleolar granules left in the cytoplasm by the rupture of the nuclear membrane. A is drawn under a higher magnification than the remaining figures, which are all to the same scale. appear to be purely of the nature of plasmosomes—, Cyclops brevicornis (Hacker, 1893). (3) The Connection between the Germinal Vesicle and Yolk Formation The co-existence in the primary oocyte of two unique cytological occurrences, namely, the germinal vesicle and the enormous growth of the cell with its formation of reserve food material, naturally suggests a causal connection between them. We have already drawn attention to the fact that the diffusion of the chromatin in the ordinary resting nucleus has the result of increasing its area in proportion to its mass, and thus of favouring active metabolism. The excessive diffusion of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabil
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