V] 



OF UNDULATINC4 MEMBRANES 



267 



which undergoes rhythmical and beautiful wavy movements. 

 When certain Trypanosomes are artificially cultivated (for instance 

 T. rotatorium, from the blood of the frog), phases of growth are 

 witnessed in which the organism has no undulating membrane, 

 but possesses a long cilium or "flagellum,'" springing from near 

 the front end, and exceeding the whole body in length*. Again, 

 in T. lewisii, when it reproduces by "multiple fission," the 

 products of this division are likewise devoid of an undulating 

 membrane, but are provided with a long free flagellum "j". It is 



Fig. 91. A, Trichomonas muris, Hartmann; B, Trichomastix serpentis, Dobell; 

 C, Trichomonas angusta, Alexeieff. (After Kofoid.) 



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 a film to run 

 up and along the flagellum, just as a soap-film would be formed in 

 similar circumstances. 



This mode of formation of the undulating membrane or frill 

 appears to be confirmed by the appearances shewn in Fig. 91. 



* Cf. Doflein, Lehrbuch der Protozoenkmide, 1911, p. 422. 



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



