THE NUCLEAR CYTOLOGY OF SIROGONIUM1,2

The nuclear cytology of 9 strains of Sirogonium is described. The interphase nucleus contains 1–3 nucleoli, a nucleolar-organizing track, and many (>100) chromocenters. During the division cycle the nucleoli are transformed into a nucleolar substance which becomes associated with the chromosome and is transported through mitosis on the chromosomes. All strains possess minute dot chromosomes varying in length at metaphase from 0.5 to 1.5 μ; satellite chromosomes are 2.5–3.5 μ long. The number of chromosomes varies from 48 ± 2 to 100 ± 2. No evidence of centromeric activity was observed.