ISSN:
1432-0878
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. The salivary gland chromosomes in all four species of Drosophila examined lie at the periphery of the nucleus, and internal to them is the nucleolus. In D. melanogaster, D. funebris and D. immigrans a chromocentre is formed and from it to the nucleolus runs a spiral thread. In D. subobscura one chromosome joins the nucleolus directly and the others are connected with it by threads from each of the synapsed mates which fuse to form one arm. 2. In all four species there is present a diffuse network of threads and granules connected with the nucleolus and the chromosomes. In D. immigrans the chromocentre is seen to be of similar constitution to this network and appears to be continuous with it, but this is probably due to the fact that the network spreads all over the nucleus. 3. The striated body of D. immigrans provides evidence that the centre of the chromocentre is still formed from the synapsis of the main chromatids, supporting the observations of the chromocentre in the other species. 4. The threads to the nucleolus from the chromosomes of D. subobscura are also formed from the main chromatid, which are euchromatic at their extreme proximal ends. 5. From this it follows that the “trabants”, known to be carried by the rod-shaped and dot-like chromosomes and probably by the V-shaped ones also, plus the non-homologous parts of the sex chromosomes, should be present outside the chromocentre, and it is suggested that the network described is formed from them. 6. In none of the species are any of the chromosomes completely inert, with the exception of the Y, nor are any branches of the V-shaped chromosomes completely inert. 7. The arms are cylindrical, and carry chromomeres throughout their thickness. 8. There has been found no constancy of position of the elements described comparable with that in the plant cells investigated by Helm.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00368251
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