Figure 2

Division processes of two G. trihymene asymmetric dividers in young cultures (A-I, J-M), other asymmetric dividers in young (N) and old cultures (O, S), and reproductive cysts (P-R). A. One four-subcell asymmetric divider. B. The first asymmetric division. Arrowhead marks the trophont to be released. C-E. The new asymmetric divider gradually became highly deformed and many cleavage furrows appeared (arrows in E). Note the three contractile vacuoles in C (arrows). F. The arrowhead, double-arrowheads and arrow show the sites of the second, third and fourth cleavage furrows respectively. G. The second asymmetric division is completed at the arrowhead. The double arrowheads show the furrow that will shortly be broken in the third asymmetric division. H. The trophont resulting from the completion of the third asymmetric division has swum out of the field of view. The fourth asymmetric division has just been completed near the arrow, at a site corresponding to the furrow indicated by the arrow in F. I. Three new asymmetric dividers (arrowheads) and one trophont (arrow) were present by the end of the fourth asymmetric division. J. One two-subcell asymmetric divider. K, L. After elongation, the first asymmetric division produced one trophont (arrow in L) and one asymmetric divider (arrowhead in L). M. The second asymmetric division, producing one trophont (arrowhead) and another asymmetric divider (arrow). N. Arrowheads mark oral apparatuses (after protargol). O. One asymmetric divider releasing a tomite (arrow). P, Q. The division process of reproductive cysts. R. Another asymmetric divider forming a cyst wall. S. An asymmetric divider resembling a dividing tomite. Scale bars: A-H: 50 μm; I: 100 μm; J-M, O-S: 25 μm.