General Morphology o£ the Protozoa 13 



origin, whereas a trailing flagellum (Fig. 1. 9, F) arises anteriorly but is 

 trailed posteriorly in swimming. A trailing flagellum may be of the con- 

 ventional type, or it may be ribbon-like as in Macrotrichomonas pulchra 

 (126). The undulating rnembrajie of Trichomonas and related genera 

 (Fig. 1. 7, G, I) contains a marginal flagellum which originates in an 

 anterior blepharoplast and extends posteriorly, sometimes beyond the end 



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c 



Fig. 1. 7. A-D. Deflandre's types of flagella: stichonematic (A), acrone- 

 matic (B). }3aiUonematic (C), pantacioneniatic (D). E. Hexarnitus pulcher, 

 flagella with rod-like basal portions; protargol; x3460 (after Kirby and 

 Honigljerg). F. Acronematic flagella of Moiiocercomonoides piUeata; pro- 

 targol; \3960 (after Kirby and Honigberg). G. Ribbon-like flagellum of 

 undulating menil,rane in Trittichomoims imiris; protargol; x2810 (after 

 Kirby and Honigberg). H. Terminal knob on flagellum of Tiypaiwsoma 

 brucei; protargol; xI790 (after Kirbv). I. Undulating membrane in Penta- 

 trichomonas honiinis; x2660 (after Wenrich). J. Axial flagellum and ribbon- 

 like transverse flagellum of Gyrodinium dorsum x470 (after Kofoid and 

 Swezy). Key: a, axostyle; c, costa; /, flagellum in undulating membrane. 



of the membrane. This marginal flagellum is sometimes ribbon-like, as in 

 Tritrichomonas muris (130). The undulating membrane of Trypanosoma 

 originates near the posterior end of the body and extends to the anterior 

 end (Fig. 1. 7, H). 



The majority of species have only one or two flagella. More than four 

 are rare in free-living flagellates, although not in parasites. When several 

 flagella are present, they may differ in size, structure, and activity. 

 Pentatrichomonas hominis (Fig. 1. 7, I), for instance, has four relatively 



