NUCLEAR GROUPS AND DIVERSITY OF MACRONUCLEI OF KENTROPHOROS-TUBIFORMIS (CILIOPHORA, KARYORELICTIDA) FROM THE JAPAN SEA

The nuclear apparatus of the Far-Eastern form of Kentrophoros tubiform is is represented by 7-12 nuclear groups, each consisting of a variabl e number of macronuclei (4-8) and micronuclei (2-4). There is no commo n membrane around individual groups. The micronuclei are filled with c ondensed chromatin and have no nucleoli and very little free karyolymp h, mainly under the envelope. The micronuclear envelope shows two memb ranes but has no pore complexes. Developing macronuclei contain numero us small chromatin bodies and, later, also small nucleoli. Adult macro nuclei are strongly variable in appearance: some have transparent kary olymph, others dark karyolymph where other components of these nuclei are poorly discernible. ''Dark'' macronuclei condense to smaller size and look pycnotic. The macronuclei, both ''light'', ''dark'' and inter mediate ones, contain several medium-sized nucleoli of compact type an d several chromocentres. Some macronuclei contain a large sphere of mi crofilamentous structure and packs of thicker fibres usually adjacent to chromocentres and/or to the sphere. The macronuclear envelope displ ays pore complexes. ''Dark'' macronuclei also often show ''blebbing'' of the nuclear envelope (with extension of the perinuclear space). In pycnotic macronuclei, only the sphere and the chromocentres remain vis ible. Condensation of some macronuclei is possibly related to their ag ing and degeneration.