1916] Swezy: The Genera Monocercomonas and Folyniastix 133 



nuclear spaces losing their staining reactions (pi. 16, fig. 8). The 

 daughter blepharoplasts move apart (pi. 17, fig. 11), but never sep- 

 arate very widely and take no further part in the division of the 

 nucleus or cell. Two new flagella appear as new outgrowths from 

 each blepharoplast. 



No definite spireme seems to be formed by the chromatin, but a 

 varying number of granules appear in the nucleus (pi. 16, fig. 8; pi. 

 17, figs. 10-12). These appear to coalesce in pairs until but two pairs 

 remain (pi. 17, fig. 12). 



A primitive spindle arrangement is noted with spindle fibers very 

 feebly developed. At the time of the eqiiatorial plate formation (pi. 

 17, fig. 13), as well as in later stages, no centrosomes are found, but a 

 small mass of chromatin is present at the poles and extends a short 

 distance along the spindle fibers (pi. 17, figs. 13-15), forming a pole 

 plate. 



As the chromatin mass on the equatorial plate separates and moves 

 toward the poles it is found that four chromosomes are present, two 

 going to each pole (pi. 17, figs. 14, 15). As the chromosomes near the 

 poles they apparently fuse with the pole plate (pi. 17, fig. 16), the 

 number of chromosomes remaining distinct until after the formation 

 of the new nuclear membrane (figs. 17, 18). 



The whole process of nuclear division takes place within the 

 nuclear membrane, including the formation of the new nuclear mem- 

 branes (pi. 17, figs. 17, 18). There is no constriction of the old mem- 

 brane, new membranes being formed around each group of chroiiio- 

 somes after they have reached the poles. This at first appears as a 

 very faint line but later, when the old nuclear membrane begins to 

 fade out, the new membranes become thicker and more distinct until 

 they have taken on the usual appearance with complete obliteration 

 of the old membrane (pi. 17, fig. 19). A similar process in nuclear 

 membrane formation is found in Hexamitus ovatus (Swezy, 1915a). 



With the reorganization of the nucleus the final steps in the process 

 of cell division take place. The parabasal body elongates with the 

 drawing apart of the daughter nuclei (pi. 17, fig. 20) and divides by 

 a simple constriction with no suggestion of mitosis in it. At the same 

 time the cytoplasm begins to divide at the anterior end (pi. 17, figs. 

 20-21), the cleft extending backward until the posterior end of the 

 body is reached and the organism separates into two daughter flagel- 

 lates. In these later stages the rhizoplasts connecting the blepharo- 

 plasts with the nuclei are frequently found, but the exact origin of 



