INTESTINAL FLAGELLATES OF RATS 129 



10(5) Five anterior flagella, one group of four attached to one 

 blepharoplast and a single one attached to a separate blepharo- 

 plast; undulating membrane extends the full length of the 

 body, but not nearly so high as in T. muris; chromatic basal 

 rod slender; axostyle slender, tapering gradually to the pos- 

 terior end which may protrude J4 to 5^ its length beyond the 

 body; no chromatic ring at the point of emergence; body 7-12 /z 

 long (Fig. 12, f) 



Pentatrichomonas sp., probably P. ardin-delteili 



11(4) Posterior flagellum not attached to body by an undulating 

 membrane; 5 anterior flagella besides the trailing flagellum; 

 axostyle slender, tapering gradually to the posterior end which 

 may protrude K to ^ its length behind the body; no chromatic 

 ring at point of emergence; 5-12 ji long (Fig. 12, e) 



Hexamastix muris 



12(1) DiPLOZOA, with bilateral symmetry 13 



13(16) With large anterior sucking disk, genus Giardia 14 



14(15) Body 7.4 to 13 (ave. lo.ii) fi. long by 5.4-9.8 (ave. 7.32) fi 

 wide; ratio L/w 1.38 (Potter, 1928) ; parabasal bodies short, 

 longitudinal and rounded at ends (Fig. 13, c) Giardia muris 



15(14) Body 9.5-18.8 (ave. 14) fi long by 5.13-10 (ave. 7.37) n wide; 

 ratio L/w 1.90 (Potter, 1928) ; parabasal bodies obliquely trans- 

 verse, slender, comma-shaped (Fig. 13, d) 



Giardia lamblia (G. intestinalis, G. enterica, G. simoni) 



16(13) With no evident anterior sucking disk, body more slender, size 



smaller, genus Hexamitus 17 



17(18) Body 7-9 fi long by 2-3 n wide, axostyles not especially chro- 

 matic, widely separated, no sharp caudal point (Fig. 13, e) 



Hexamitus muris 



18(17) Body 7-10 /i long by 3-5 yL wide, axostyles chromatic, appar- 

 ently fused through most of their length; sharp caudal point 

 (Fig. 13, f) Hexamitus pulcher 



3. Some problems of flagellate organization 



There are many interesting problems in connection with the 

 organization of these intestinal flagellates, only a few of which will 

 be mentioned. For example, satisfactory conclusions have not 

 been reached in regard to the real nature and functions of the 

 axostyle, the chromatic basal rod, the parastyle, the parabasal body 

 or the various groups of chromatic granules. Since Grasse (1926) 

 has given an extended discussion of these problems, it will be sufTfi- 

 cient to discuss them very briefly here. 



The axostyle. In the trichomonads of the rat there are two types 

 of axostyle. T. muris and T. minuta have axostyles that are hyaline, 

 of uniform diameter through the body, tapering rapidly to a sharp 



