Inhaltsangabe
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 Excerpt: ... passed into the protoplasm, while the remainder is in process of dissolution. In what manner the nuclear material dispersed in the protoplasm becomes fashioned into the small nuclei of the later stage I have no evidence to show. rhumbler has recently published an account (28, b) of his investigation of Saccammina sphwrica (M. Sars), in which he has obtained a much more complete history of some of the nuclear changes than I have succeeded in doing. Rhumbler shows that the large solitary nucleus of this species is gradually altered during its growth. The Binnenkorper, the nucleoli of other authors, which in young specimens are few, large and frequently compound, after increasing in numbers at first, become in the later stages fewer or disappear altogether. Meanwhile chromatin granules appear in the nucleus, and increase in numbers, becoming embedded in linin fibres. In the course of development, the substance between the Binnenkorper, which is at first homogeneous, becomes vacuolated and then formed into a well-marked reticulum (Wcibenwerk) which appears first at the centre, and gradually extends to the periphery of the nucleus. Finally, the nuclear wall, which has been very distinct in previous stages, disappears, and the linin fibres with the chromatin grains are dispersed in the protoplasm. It is suggested that the last stage of this process is preparatory to reproduction. There are clearly several points of resemblance between the nuclear changes of Saceammina and those of the megalospheric form of Polystomella. I find, on referring to my specimens, that minute granules are frequently present in the reticulum, which may very possibly be grains of chromatin, though they are not seen so distinctly as in the very large nuclei described by Rhumbler. On the o...
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Reseña del editor
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 Excerpt: ... passed into the protoplasm, while the remainder is in process of dissolution. In what manner the nuclear material dispersed in the protoplasm becomes fashioned into the small nuclei of the later stage I have no evidence to show. rhumbler has recently published an account (28, b) of his investigation of Saccammina sphwrica (M. Sars), in which he has obtained a much more complete history of some of the nuclear changes than I have succeeded in doing. Rhumbler shows that the large solitary nucleus of this species is gradually altered during its growth. The Binnenkorper, the nucleoli of other authors, which in young specimens are few, large and frequently compound, after increasing in numbers at first, become in the later stages fewer or disappear altogether. Meanwhile chromatin granules appear in the nucleus, and increase in numbers, becoming embedded in linin fibres. In the course of development, the substance between the Binnenkorper, which is at first homogeneous, becomes vacuolated and then formed into a well-marked reticulum (Wcibenwerk) which appears first at the centre, and gradually extends to the periphery of the nucleus. Finally, the nuclear wall, which has been very distinct in previous stages, disappears, and the linin fibres with the chromatin grains are dispersed in the protoplasm. It is suggested that the last stage of this process is preparatory to reproduction. There are clearly several points of resemblance between the nuclear changes of Saceammina and those of the megalospheric form of Polystomella. I find, on referring to my specimens, that minute granules are frequently present in the reticulum, which may very possibly be grains of chromatin, though they are not seen so distinctly as in the very large nuclei described by Rhumbler. On the o...
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