622 FAMILY: CHILOMASTIGIDiE 



tunensis are almost certainly identical with Chilomastix mesnili, though Gabel failed 

 to recognize the flagellum within the cytostome. The flagellates belonging to the 

 genus Enleiomonas established by Fonseca (1915) are probably, in some cases at 

 least, small rounded forms of CMlomastix (see p. 307). 



C. ?nesnili is usually about 10 to 15 microns in length, though very 

 small spherical forms not more than 3 to 4 microns in diameter may be 

 met with as well as larger ones up to 20 microns in length (Fig. 256). The 

 anterior end is rounded or sometimes definitely flattened, while the 

 posterior end varies considerably. It is sometimes blunt, and at other 

 times drawn out into a long thin tapering tail. There is a long cytostomal 

 cleft about half as long as the body itself, and this is obliquely arranged in 

 such a way that, if a flagellate is observed with the cytostomal cleft 

 upwards, the rounded anterior end pointing away from the observer and 

 the posterior end towards him, then the anterior end of the cytostomal 

 cleft is nearer the left side of the body of the flagellate, while the posterior 

 end is nearer the right side. The two margins of the cytostomal cleft 

 often form definite lips, which may even overlap one another. There is 

 also a groove on the body which varies in development in different indi- 

 viduals. If the flagellate be regarded as in the position indicated above, 

 then the groove commences near the anterior end of the body to the left 

 of the cytostomal cleft, and passes round the body in a spiral manner 

 parallel to the cleft (Fig. 256, 9-10). It may terminate at the posterior 

 end of the cytostomal cleft, but is often continued beyond it, and may 

 make two complete turns of the body. On account of this spiral groove, 

 many of the flagellates appear to have the posterior region of the body 

 curiously twisted. In some infections the spiral groove is not evident. 

 There is a spherical nucleus near the anterior end of the body, and just 

 anterior to it is a group of blepharoplasts, which, according to Dobell 

 (Dobell and O'Connor, 1921) are six in number. The cytostomal cleft 

 commences just behind the group of blepharoplasts. Three of the 

 blepharoplasts are in front of the others, and from each of these there 

 arises an axoneme which passes to the anterior surface of the body, there 

 to enter one of the three anteriorly directed flagella. Each flagellum is 

 about as long as the body. The three posterior blepharoplasts give rise 

 to three different structures. The central one gives rise to a flagellum, 

 which is thicker than the anterior flagella, and which lies in the cytostomal 

 cleft. Some observers, as, for instance, Boeck (1921a), believe that there is 

 a membrane within the cytostomal cleft, and that the flagellum is attached 

 to its margin. This is probably not correct, as sometimes the flagellum 

 leaves the cytostomal cleft in which it usually lies. If the flagellate is 

 observed in the position described above, it will be noted that of the three 

 posterior blepharoplasts that on the left gives rise to a deeply staining fibre, 



