1920] Kofmd-Swezy: Morphology and Mitosis of Chilomastix 135 



Qg. 19). Ill the equatorial plate stage (pi. 17, &g. 18) the chromosomes 

 appear a-s large, dense rounded masses, connected with the centrosomes 

 at the poles hy numerous spindle fibers. The number of these granules 

 or chromosomes is rather difficult to determine at this stage, but in 

 the anaphase (fig. 20) five were clearly distinguishable. They vary 

 considerably in size, and stain intenselj' with iron haematoxylin. 

 The spindle fibers disappear as the chromosomes move to the poles 

 (pi. 17, fig. 22) and each granule becomes elongated in a narrow cone 

 at its point of attiichment to the pole of the nucleus where the centro- 

 some lies. 



In the reorganization of the nuclei the chromatin is found massed 

 in groups of rather large granules at the center of the nucleus (pi. 17, 

 fig. 24). Later the chromatin takes on the form of a small compact 

 karyosome connected with the periphery by narrow fibers and the 

 remainder of the chromatin collects on the nuclear membrane (pi. 17, 

 fig. 23). 



The plane of division of Chilom-astix is morphologically longitud- 

 inal. This is shown in the prophase in the splitting of the blepharo- 

 plasts and their separation (pi. 16, figs. 13-15; pi. 17, figs. 16, 17). 

 With the formation of the relatively large spindle in the rigid confines 

 of the cyst some adaptation is necessary for the accommodation of the 

 two schizonts. This adaptation appears in the initial posterior migra- 

 tion of one of the centrosomes carrying with it the newl}^ formed 

 neuromotor apparatus, resulting in an apparently transverse division 

 of the nucleus (pi. 17, figs. 19-22). 



It is probable that one or two other nuclear divisions follow in the 

 cysts, though we have not been able as yet to fibad them in infected 

 stools in which we have secured the first division by keeping the 

 stools for as much as four days at room temperatures. 



DISCUSSION 



Chilomastix is asymmetrical in the distribution and function of 

 the anterior flagella, in the location and organization of the neuro- 

 motor apparatus, and in the course of the spiral groove. This groove 

 has the same torsion as the transverse flagellum and girdle of the 

 dinoflagellates and the undulating membrane of Trichommias. This 

 torsion is sinistral. It has the same twist as the thread of a left-handed 

 screw. 



