430 



THE FORMS OF CELLS 



[CH. 



devoid of an undulating membrane, but are provided with a long 

 free flagellum*. It is a plausible assumption to suppose that, as 

 the flagellum waves about, it comes to lie near and parallel to the 

 body of the cell, and that the frill or undulating membrane is formed 

 by the clear, fluid protoplasm of the surface layer springing up in 



Fig. 141. A, Trichomonas muris Hartmann; B, Trichomastix serpentis DobeU; 

 C, Trichomonas angusta Alexeieff. After Kofoid. 



Fig. 142. A "Trypanosome. 



a film to run up and along the flagellum, just as a soap-film would 

 form under similar circumstances. 



This mode of formation of the undulating membrane or frill 

 appears to be confirmed by the appearances shewn in Fig, 14L 

 Here we have three little organisms closely allied to the ordinary 

 Trypanosomes, of which one, Trichomastix (B), possesses four 

 flagella, and the other two. Trichomonas, apparently three only: 



* Cf. Minchin, Introduction to the Study of the Protozoa, 1914, p. 293, Fig. 127. 



