300 FAMILY: MONADID^ 



before entering the flagellum. The genus Bodo includes flagellates which 

 also have two flagella, but the axonenies of these arise from two blepharo- 

 plasts which are separated from the nuclear membrane, and which have a 

 parabasal body associated with them. There seems to be no justification 

 whatever for Ndller's (1922) inclusion in the same genus of flagellates of 

 the Cercomonas type with adherent axoneme and those of the Heteromita 

 (Cercobodo) type, much less for his assumption that they all belong to the 

 Rhizojjoda. 



Heteromita uncinata Kent, 1880. — This was one of the flagellates 

 studied by Dallinger and Drysdale (1873), who accurately described the 

 main features of its life-cycle. What appears to be this organism was 

 seen by the writer as a coprozoic flagellate in old human faeces. It is 

 pear-shaped, with a rounded posterior end and somewhat pointed anterior 

 end (Fig. 142). It varies in length as a rule from about 3 to 8 microns, 

 but exceptionally large forms up to 10 microns in length occur, A con- 

 tractile vacuole is present in the hinder region of the body, and there is no 

 cytostome. Arising from the pointed anterior end are two flagella of 

 unequal length. The shorter, which is slightly thicker than the other, is 

 approximately as long as the body, and directed forwards during progres- 

 sion. The longer flagellum, two to four times the length of the shorter 

 one, performs wide sweeping movements in front of the flagellate when it is 

 swimming freely. If the long flagellum comes in contact with the glass, 

 the flagellate still moves forwards by the action of the shorter flagellum, 

 while the long one trails behind over the surface. In stained individuals, 

 the axonenies of the two flagella can be traced to the surface of the nuclear 

 membrane, which may be drawn out into a cone at the point of union 

 (Fig. 68). In some individuals, two blepharoplasts can be distinguished 

 at the apex of the cone. The centre of the nucleus is occupied by a large 

 karyosome. In the free-swimming condition the body of the flagellate 

 retains its pear shape, but if it comes in contact with a surface it exhibits 

 amoeboid changes of shape. In pure cultures reared from a single 

 flagellate there occur amoeboid forms devoid of flagella, so that a definite 

 amoeboid phase has to be recognized. When grown on agar plates there 

 occur much larger multinucleated forms, with a corresponding number of 

 contractile vacuoles and pairs of flagella. Dallinger and Drysdale de- 

 scribed the fusion of numerous flagellates to form a multinucleated body. 

 That the multinucleated forms which occur on agar plates do not always 

 arise in this way is shown by the fact that, after staining, they may have 

 all their nuclei in process of division, the body containing a number of 

 spindles. These multinucleated forms, as they occur on agar plates, are to 

 be regarded as instances of delayed division of the cytoplasm. 



The flagellate reproduces by longitudinal division in the free-living 



