On the Chromocentre Observed Through the Mitotic Cycle of Somatic Cells in Drosophila virilis

Abstract

The mitotic chromosomes of Drosophila virilis observed in the oesophageal ganglion cells are longitudinally differentiated as regards the structure into two kinds of chromatin-heterochromatin and euchromatin. The proximal halves of chromosomes adjacent to the spindle attachment regions which are composed of heterochromatin remain chromatic and fail to disintegrate during the interphase, while the distal halves consist of euchromatin, with the exception of the Y chromosome which is totally heteropycnotic. Observations made through the mitotic cycle showed that it is those heterochromatic regions which fuse, including the Y chromosome, to form the chromocentre right through the telophase to prophase. Some remarks on the relation between the chromocentre of the salivary gland nucleus and that of the mitotic nucleus are given.