OM-fluorescence microscopy (Fig. 39) proved that these chromosomes have probably two centromeres appearing as fluorescing spots. Due to their positions close to each other they behave functionally as a single centromere (Fig. 59 shows a bivalent at meiosis), thus prohibiting further chromosome differentiation by bridge formation and breakage at mitosis. Heteromorphism may occur in many of the chromosome pairs. The chromosome diagrams (Fig. 4-9) show that the 2n= 30 specimens of C. z~ylunicwm are diploids. Except for the ZI population the other population