32 



MORPHOLOGY OF PROTOZOA 



portion. For the former the name rhizoplast is often employed. When 

 an organism is developing a flagellum, a blepharoplast first becomes 

 apparent in the cytoplasm, and an axoneme is formed as an outgrowth 

 from it. When the surface of the body is reached, increase in length still 

 takes place, the axoneme pushing out a thin covering of cytoplasm. It is 

 probable that the axial rod of an axopodium is a homologue of the axoneme 

 of a flagellum. 



The flagella of the Mastigophora vary in number. In the typical forms 

 they are not numerous. There may be only a single one, or as many as 

 eight. They arise most usually from the anterior end of the body, and 

 are directed forwards. By their lashing movements they propel the 

 organism through the medium. In some instances certain flagella arise 

 from the posterior end of the body, and are directed backwards. Thus, 

 in Hexamita two of the eight flagella are posterior in position, but their 

 axonemes can be traced through the cytoplasm to the anteriorly situated 



blepharoplasts (Fig. 288). In other 

 cases, as in Tricercomonas and Cerco- 

 monas, the axonemes of the posterior 

 flagellum can be traced over the surface 

 of the body to the anterior end, where it 

 enters the cytoplasm and passes to the 

 blepharoplast (Figs. 259 and 261). In 

 the flagellates of the genera Trypano- 

 plasma and Trichomonas such a back- 

 wardly directed axoneme is adherent to, 

 or embedded in, the margin of a thin 

 band of cytoplasm, the undulating mem- 

 brane (Figs. 26 and 151). In other cases, such as Bodo, one flagellum is 

 directed backwards, and acts as a trailing flagellum without being attached 

 to the surface of the body (Figs. 21 and 33). In the case of the trypano- 

 somes, the blepharoplast occupies an unusual position at the posterior 

 end of the body. The axoneme arising from it is directed forwards, and 

 passes over the surface of the body or along the margin of an undulating 

 membrane as far as the anterior end of the body, where it either terminates 

 or becomes a flagellum (Fig. 28, B). 



All the flagella possessed by a flagellate may be uniform as regards 

 length and thickness when they fulfil the same function. Frequently, 

 however, variations occur. In the case of E^nbadomorias, one of the two 

 flagella, which organisms of this genus possess, is associated with the 

 cytostome, and is much thicker and shorter, and performs more regular 

 undulating movements than the anteriorly directed one (Fig. 11). 

 Flagella are employed not only for purposes of progression, but also for 



Fig. \\.~Enibadomonas sp. from 

 Culture of Intestinal Con- 

 tents OF Testudo argentina 

 ( X ca. 1,500). (Original.) 



