University of California Publications in Zoology [Vol. 16 



has. gr. 



and Wenyon (1913) call this region the cytopharynx. Wenyon de- 

 scribes an additional structure, a slit-like groove leading into the so- 

 called cytopharynx; this he calls a cytostome, believing that bacteria 

 pass through the cytostome and cytopharynx into the endoplasm of 

 the posterior part of the body. Such a striicture 

 and function has not been noted in the study 

 of Crithidia leptocoridis. 



The nucleus (trophonucleus) of the flagellate 

 of the vegetative phase has a diameter from 1 to 

 1.5 IX, almost equal to the width (pi. 3, figs. 58-62) 

 of the body and lies in a central position or just 

 above the center in the anterior half of the organ- 

 ism (pi. 3, fig. 62). A distinct nuclear mem- 

 brane (pi. 3. figs. 57, 59, and 62) is always 

 present. The distribution of the chromatin 

 material within the nuclear membrane is subject 

 to much variation in the elongate flagellates of 

 the vegetative phase. Probably the most char- 

 acteristic disposal of the chromatin is in the 

 form of a single central granule or karyosome 

 (pi. 2, figs. 54-56; pi. 3, figs. 57, 58). As seen 

 in plate 3, figures 60 and 62, the chromatin is 

 in three elongate granules. Patton (1908) and 

 Porter (1909) foimd the chromatin in some forms 

 of Crithidia gerridis in eight chromatin granules 

 or chromosomes. This will be discussed in more 

 detail later in connection with longitudinal 

 division. 



The extranuclear organelles, as previously 

 mentioned, consist of the ' ' kinetonucleus, ' ' rhizo- 

 plast, flagelluin, basal granule, and the ' ' axostyle ' ' 

 (text fig. A). The "kinetonucleus" has always 

 been found anterior to the nucleus. In the vegetative phase the distance 

 between the nucleus and the "kinetonucleus" varies from 1.5 fx (pi. 2, 

 figs. 54 and 55) to 5 /i (pi. 3, figs. 57-62). In stained preparations the 

 "kinetonucleus" presents an exceedingly clear-cut outline, since it 

 stains deeply and lies in an area of lightly stained cytoplasm (pi. 2, 

 fig. 55). It is made up of two relatively large chromatin granules 

 lying in clo.se proximity (pi. 2, figs. 54-56). Looking from a certain 

 angle these two chromatin granules have the appearance of a single 



ckr.gr. 



Fig. A. Lateral 

 view of Crithidia lep- 

 tocoridis to show the 

 nucleus and extra-nu- 

 clear organelles. X 

 1800. ax., axostyle; 

 bas. gr., basal granule ; 

 chr. gr., chromatin 

 granule; ^., flageUum; 

 n., nucleus; rlx., rhizo- 

 plast; und. m., undu- 

 lating membrane ; vac, 

 vaeuole-like area about 

 the "kinetonucleus." 



