1989 年 54 巻 2 号 p. 255-262
Karyological investigations accomplished on sixteen local isolates of Phacus revealed the structure and pattern of mitotic division of nuclei to be atypical. The chromosome numbers ranged from n=10 in P. cylindrus to n=226±8 in P. longicauda, representing the widest range of chromosome numbers reported so far for euglenoid flagellates. All the chromosome counts made in this study proved to be new to science. Cases of the existence of cytological races are well-documented. The possible role of chromosomal rearrangements, euploidy and more specifically aneuploidy in speciation of the genus is suggested.