. The cell; outlines of general anatomy and physiology. t they probably represent the equatorial plates of plants,which are much better developed. b. Division of the egg-cells of A scans megalocephala and Toxopneustes liuidus. The nuclei of the eggs of Ascaris are re-markable for the size and distinctness of their centrosomes, and for the small number of their nuclear segments, of which in one species only four, and in another only two, are present. Another very important phenomenon, the multi-plication of the centrosomes by division, may be especially clearly seen in this object. It is best t
. The cell; outlines of general anatomy and physiology. t they probably represent the equatorial plates of plants,which are much better developed. b. Division of the egg-cells of A scans megalocephala and Toxopneustes liuidus. The nuclei of the eggs of Ascaris are re-markable for the size and distinctness of their centrosomes, and for the small number of their nuclear segments, of which in one species only four, and in another only two, are present. Another very important phenomenon, the multi-plication of the centrosomes by division, may be especially clearly seen in this object. It is best to commence our in-vestigations at that point when the egg has just developed the furrow, and when the four nuclear loops on either side of the plane of division have transformed themselves into a vesicular nucleus of irregular outline (Fig. 82). The side of the nucleus, which is directed towards the pole, has several ragged processes, the nuclein being spread out upon its loose network. The centrosome may still be distinguished in the neighbourhood of. Fig. 82. — Egg of Ascarismegalocephala undergoing theprocess of double are resting; the cen-trosomes as yet undivided.(After Boveri, PI. IV., Fig. 74.) 190 THE CELL what was formerly the pole of the division figure; it is enclosedin granular protoplasm, which contracts with the yolk substanceof the egg, and has been named by van Beneden the attractionsphere, and by Boveri the archoplasm. Before the nucleus has quite returned to the resting condition,and even sometimes before the first division is completed, it com-mences to make preparations to divide a second time ; these startwith changes in the centrosome (Fig. 84), which extends itself
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Keywords: ., bookcentury1800, bookdecade1890, bookidcelloutlines, bookyear1895
