294 ELERY R. BECKER. 



large numbers in all ground squirrels examined. The body is 

 elliptical, with a pointed posterior end, due to the protruding 

 axostyle (Fig. 19). Length is from 6.5 to 10 micra without the 

 axostyle which protrudes from 2 to 3 micra beyond the body. 

 The nucleus lies at the anterior end. In the resting stage there 

 is a round central chromatic endosome, an achromatic nuclear 

 membrane, with a space between the endosome and membrane 

 which is clear except for a sprinkling of fine granules. The 

 endosome is prominently visible even in living unstained speci- 

 mens. A large deeply staining basal body lies anterior to the 

 nucleus. From it arise an axostyle which curves about the 

 nucleus, and passes to the posterior end of the body; three an- 

 terior flagella; and a fourth flagellum which is directed toward 

 the posterior. It lies in close contact with the body for about 

 half the length of the cell, and the remaining length trails behind. 



Typically, members of the genus Trichomonas possess an 

 undulating membrane with a chromatic basal rod; e.g., Tricho- 

 monas muris. This flagellate possesses no true undulating 

 membrane, since the posterior flagellum which is the homologue 

 of the marginal flagellum lies close to the body. It vibrates only 

 slightly in the anterior region, while the free posterior end is quite 

 active. Stained preparations show no chromatic basal rod. 

 Whether these differences are sufficient to create a new genus is 

 doubtful. Stained preparations often show a large open cyto- 

 stome (Fig. 17). In living preparations it is usually closed. 



Very few dividing forms were found, and hence no chromosome 

 counts were made. Sometimes this flagellate is parasitized by a 

 Sphaerita (Fig. 19). 



Tetratrichomastix citelli sp. nov. This flagellate (Figs. 16, 18) 

 was present in nineteen of the twenty ground squirrels. The 

 body is irregularly pyriform, but approximately bilaterally 

 symmetrical, due to a slight indentation just behind the anterior 

 tip of the body from which the flagella leave the body. The 

 axostyle protrudes from the posterior tip of the body. The body 

 length, exclusive of axostyle, ranges from 7 to 13 micra. The 

 axostyle often extends 2 to 4 micra beyond the body. The 

 flagella are five in number, four anterior ones which beat back- 

 wards in unison, with lashing strokes, and a schleppgeisel, which 



