MORPHOLOGY 



47 



flagellum, in Mallomonas, Chromulina, Trachelomonas, Urceolus 

 (/), Phaciis, Euglena, Astasia, Distigma, etc.; and both kinds in 

 Synura, Uroglena, Dinobryon, Monas (g), etc. (Vik). 



The flagellum is most frequently inserted near the anterior end 

 of the body and directed forward, its movement pulling the organ- 

 ism forward. Combined with this, there may be a trailing flagellum 

 which is directed posteriorly and serves to steer the course of move- 

 ment or to push the body forward to a certain extent. In a compara- 

 tively small number of flagellates, the flagellum is inserted near the 



Flagellum 



Undulating 

 membrane 



Nucleus 



Anterior flagellum 



Basal granule 

 Blepharoplast 

 Rhizoplast 

 Nucleus 



Parabasal body 



Basal granule 

 m Blepharoplast f^7^ Posterior flagellum 



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

 a, Trypanosoma brucei; b, Proteromonas lacertae. 



posterior end of the body and would push the body forward by its 

 vibration. Lankester coined the terms tractella and pulsella for 

 pulling and pushing flagella respectively. 



In certain parasitic Mastigophora, such as Trypanosoma (Fig. 

 9, a). 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 rotatorium of the 

 frog, and is called the undulating membrane. In many of the dino- 

 flagellates, the transverse flagellum seems to be similarly constructed 

 (Kofoid and Swezy) (Fig. 107, d,f). 



Cilia. The cilia are the organella of locomotion found in the Cilio- 

 phora. They aid in the ingestion of food and serve often as a tactile 

 organella. The cilia are fine and more or less short processes of ecto- 

 plasm and occur in large numbers in the majority of the Holotricha. 



