LONGITUDINAL AND TRANSVERSE DIVISION IN TWO CLOSELY RELATED FLAGELLATES

Abstract

Spirotrichonympha polygym Cupp, 1930 from Kalotermes (Paraneotermes) simplicicornis actually included 2 spp. of hypermastigote flagellates. S. polygyra has 4 flagellar bands, which arise anteriorly in 2 groups. The flagella arise in pairs, from paired basal granules along the bands. The axostyle is fibrillar. The structures that are probably parabasal bodies are spherical, are arranged between the bands for their whole length posterior to the nucleus, and are probably connected to the bands. Between the bands also are granules, which probably arise from the bands, and extend anteriorly beyond the parabasals. The chromosomes are duplicated in the late telophase; a short and a long pair persist through the interphase. Each chromosome consists of a spiraled filament and a sheath; each is anchored at one end to the nuclear membrane and is attached at the other end to a chromatin nucleolus or a part of one. In mitosis the flagellar bands separate in pairs and unwind, and the fibers of the broad central spindle form between the bands near the anterior end. An elongate centriole follows one band of each group, as a line difficult to separate from the band. Some astral rays come in contact with the intranuclear chromosomal fibers and move the chromosomes, which become shorter and broader, toward the poles. The direction of the spindle is transverse; cytoplasmic division is longitudinal. The 2d species, S. bispira*, is similar to the other except that there are 2 flagellar bands. In the 2 interphase chromosomes each sheath contains 2 coils. The coil has divided in the late telophase, but the sheath does not divide until the beginning of the next nuclear division. The elongate centriole follows one band for 4 or 5 spirals; sometimes its posterior part is separated. A new flagellar band, with a centriole closely following it, develops from the point of origin of the parent bands, then breaks loose and migrates posteriorly, developing basal granules and flagella. Astral rays grow from the distal part of each centriole, meet, join, overlap and grow along one another to form the central spindle. What was the anterior end of the new band eventually reaches the posterior end of the body. In this migration it has drawn the spindle out longitudinally, and the astral rays that become long extranuclear chromosomal fibers carry 1 chromosome of each pair posteriorly. The new flagellar band arranges itself in a spiral, and new extranuclear organelles develop, the anterior daughter having retained all the parent organelles except the axostyle, which is resorbed. Transverse cytoplasmic division occurs. The posterior daughter is at first considerably smaller than the anterior one. After separation the 2d flagellar band grows out.