46 



PROTOZOOLOGY 



crassicauda, Trcpomonas rotans, T. agilis, Hexamita injlata, 

 Urophagus rostratus, etc.; the ciliary flagcllum, in JMallomonas, 

 Chromulina, Trachclomonas, Urccolus (/), Phaciis, Euglena, 

 Astasia, Distigma, etc.; and both kinds in Syniira, Uroglena, 

 Dinobryon, Monas (g), etc. 



The flagcllum is most frequently inserted near the anterior end 

 of the body and directed forward, its movement pulling the 

 organism forward. Combined with this, there may be a trailing 

 flagellum which is directed i)osteriorly and which serves to steer 



Fliigellum 



Undulatinji 

 membrane 



Nucleus 



Basal granule 

 Blepharoplast 



Anterior flagellum 



Basal granule 

 Blepharoplast 

 Rhizoplast 

 Nucleus 



Parabasal body 



Posterior flagellum 



Fig. 9. Diagrams of two flagellates, showing their structures (Kiihn). 

 a, Trypanosoma brucei; b, Proteromonas lacertae. 



the course of movement or to push the body forward to a certain 

 extent. In a comparatively small niunber of flagellates, the flagel- 

 lum is inserted near the posterior end of the body and would push 

 the body forward by its -snbration. Lankester coined tractella 

 and pulsella for pulling and pushing flagella respectively. 



In certain parasitic Mastigophora, such as Trjrpanosoma (Fig. 

 9, o), Trichomonas, etc., there is a very delicate membrane 

 extending out from the side of the body, a flagellum bordering 

 its outer margin. When this membrane vibrates, it shows a 

 characteristic undulating movement, as will easily be seen in 

 Trypanosoma rotaforiutn of the frog, and is called the undulating 

 membrane. In many of the dinoflagellates, the transverse flagel- 

 lum seems to be similarly constructed (Kofoid and Swezy) 

 (Fig. 101, d, /). 



