HETEROMITA UNCINATA 301 



condition, but most usually after having become spherical and quiescent. 

 The amoeboid forms without flagella also multiply by binary fission. The 

 blepharoplasts on the nuclear membrane divide, and the two pairs of 

 daughter blepharoplasts take up positions at opposite poles of the elongat- 

 ing nuclear membrane (Fig. 68). Two new axonemes grow out from two 

 of the daughter blepharoplasts, and these form flagella at the surface of 

 the body as division is proceeding. The karyosome of the nucleus breaks 

 up, and a small number of chromosomes appears at the equator of the 

 spindle which forms within the nuclear membrane between the blepharo- 

 plasts. Daughter plates are formed by division of the chromosomes, and 

 a long spindle stretches across the elongated body of the flagellate. The 

 daughter plates approach the blepharoplasts, the intermediate part of the 

 spindle disappears, and the nuclear membrane closes round the daughter 

 chromosomes, which concentrate into the characteristic karyosomes. The 

 cytoplasm now becomes constricted and divided into two parts, and two 

 flagellates result. Division of the amoeboid forms takes place in the same 

 manner except for the absence of flagella. 



Under adverse conditions the flagellate loses its flagella, becomes 

 spherical and encysts in spherical cysts 3 to 6 microns in diameter. The 

 cyst wall appears perfectly smooth and shows no indication of pores. 

 On agar plates larger spherical, ovoid, or more irregularly shaped cysts up 

 to 10 microns in diameter occur. As the included cytoplasm may contain 

 as many as sixteen nuclei, it is probable they are formed by the encystment 

 of the multinucleated forms which occur in these cultures. The emergence 

 from the cysts of large numbers of minute flagellates and the conjugation of 

 two individuals, as described by Dallinger and Drysdale, were not observed. 



The life-history and structure of this flagellate is of interest in that it 

 closely resembles Cercomonas longicauda, another coprozoic organism 

 (Fig. 259). It differs chiefly in the fact that both flagella arise at the 

 anterior end of the body, there being no tendency for one of the axonemes 

 to pass along the surface of the body before entering a flagellum. The 

 amoeboid forms of C. longicauda retain the two flagella, while those of 

 H. uncinata usually discard them. 



It seems not improbable that the flagellate which Sangiorgi (1922a) 

 cultivated from human faeces, and which he named Pirobodo intestinalis, 

 belongs to the genus Heteromita. As described, it had a pear-shaped 

 body with two long flagella arising from the pointed anterior end. The 

 dimensions given are 12-8 to 16-6 microns for the length and 9-6 to 14-4 

 for the breadth. The description is, however, so inadequate that it is 

 impossible to identify the organism with any degree of accuracy. 



