1920] Kofaid-Sivczy : Morphology and Mitosis of Chilomastix 121 



to 15/i, having contracted in the process of fixation. The small forms, 

 Sjj. in length, noted by Prowazek and Werner (1914), Wenyon (1915), 

 and Chalmei-s and Pekkola (1918), may be Chilomastix. "We find 

 such small forms with the larger ones but have not been able to prove 

 critically that they are Chilom-astix. 



The cytoplasm of Chilomastix is enclosed in a very resistant, elastic 

 pellicle, which permits rapid changes in contour and deformation. 

 It is crowded in the active stage with vacuoles of varying size, some 

 of which contain bacteria (pi. 15, fig. 4), though generally they show 

 only a fluid material. We find no evidence of a specialized region 

 of ingestion in the cytostomal pouch, though the locality where the 

 parastjie and parabasal are in juxtaposition is apparently adapted to 

 this end. There is no specialized structure for the elimination of 

 dejecta. This appears to be accomplished, in some instances, by the 

 autotomy of cytoplasm and its contents at the posterior tip. In one 

 instance a long rod-shaped bacillus was seen lying transvei-sely in 

 such a terminal mass. 



The spiral groove {spir. gr., figs. A, B) is a peripheral modification 

 of the cytoplasm, seemingly peculiar to the genus Chilomastix, which 

 is intimately connected with the very evident torsion of the body in 

 the active flagellate stage. It is a special trough or channel impressed 

 in the cytoplasm of the body, running from the dorsal face of the 

 anterior end posteriorly in a spiral course from the mid-doi-sal to the 

 right side and obliquely across the ventral face to the left, making 

 approximately a full turn in its sinistral course. This trough in 

 contracted, stained individuals is a narrow, shallow channel about 

 0.25 of the diameter of the nucleus in width (pi. 15, fig. 1). In active 

 flagellates it may be a deep, wide trough, which may be as wide as 

 the nucleus anteriorly and cleave the body for nearly a third of its 

 diameter, or it may be a narrow depression tapering posteriorly and 

 terminating near the very tip. The floor of this groove is somewhat 

 less coai"sely granular than the rest of the peripheral cytoplasm. It 

 is evidently a contractile area varying in the depth of its indentation. 

 In the cyst {spir. gr., fig. B; pi. 16, fig. 10) it is a meridional, faintly 

 marked, clear streak on the right side of the nucleus and cj-tostome, 

 running nearly from pole to pole. It appears to have lost entirely 

 all trace of the torsion of the active flagellate stage after the encysted 

 phase is established. 



The nucleus (nuc, fig. A) is a spheroidal, rarely ellipsoidal, struc- 

 ture located close to the anterior border of the bodv in the active 



