1973 年 38 巻 4 号 p. 687-697
DNA synthesis has been studied with TH3 in the terminal S stage of the species O. americanus (2n and 4n), O. cultripes (2n), and the artificial triploid hybrid of O. cultripes×O. americanus. A slight asynchrony was observed between homo-logues, more accentuated in the tetraploid and in the triploid species. Chromosomes of either late or early replication were not observed. Variations in the G2+P period in mitotic cells were observed in all the species, always of a longer duration in gonads. The satellites in pair 11, present in all species studied, are early re-plicating, but the satellite of pair 4 in O. americanus 2n, is late replicating.