ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. Nurse cells in the ovary ofD. melanogaster show a range in nuclear diameters of from 5μ to 40μ. This indicates that the volume of the smallest nuclei must have been doubled 8 times to produce the largest nuclei which are therefore at least 512-ploid. 2. In nuclei with the same diameters we find evidence of a series of nuclear changes paralleling ordinary mitosis from a diffuse resting stage to a late prophase condition of the chromosomes. No equitorial plate is formed, nor is there an anaphase movement of the chromosomes, and throughout the cycle the nuclear wall remains in-tact.Geitlers term “endomitosis” is used to describe this inner division cycle of the chromosomes. 3. A striking feature of the endomitotic cycles, inDrosophila ovaries, is the tendency for the chromatids to collect around separate centers in what correspond to early and late prophase stages. In the latter the association is most intimate. 4. In the earlier endomitotic cycles, the association between chromatids is extremely close, and in the late prophase dense chromosome-like aggregates of eight threads are found. In later cycles the association, is less intimate. 5. Five division cycles are figured but from volume considerations, it is concluded that eight must occur to form the largest nuclei, if, as seems very probable, with each division cycle there is a doubling of the nuclear volume.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01271636
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