Figure legend

FIGURE 11. A trophozoite of P. fallax showing the beginning of nuclear division. Spindle fibers (Sf) crossing from one nuclear pole (Np) to the other can be observed. The nuclear envelope appears to remain intact except around the region closely associated with the poles of spindle fibers. X 47000.

Figure notes

A process of schizogony begins early in the growth of the trophozoites. Nuclear division appears to initiate this process before any other significant cytoplasmic changes take place. One of the most noticeable changes during the nuclear division is the appearance of spindle fibers within the nucleus (Figs. 11-13). The spindle fibers are composed of several micro tubules, measuring 200-220 A in diameter and running from one nuclear pole to the other. In the nuclear division the nuclear membrane is preserved except around the region closely associated with the poles of spindle fibers (Fig. 11).