MORPHOLOGY AND PHYSIOLOGY 



27 



certain internal changes an amoeba may show conspicuous dif- 

 ferences in pseudopodia (Neresheimer). Pseudopodia occur 

 widely in forms which are placed under classes other than 

 Sarcodina during a part of their life-cycle. Care, therefore, 

 should be exercised in using them in taxonomic consideration of 

 the Protozoa. 



Fiagella are filamentous extensions of the cytoplasm. Or- 

 dinarily they are extremely fine and highly vibratile, so that it is 

 difficult to see them in life under the microscope with a moderate 

 magnification. In a comparatively small number of species the 

 flagellum can be seen distinctly in life as a long filament, as for 

 example in Peranema (Fig. 42). As a rule, the number of fiagella 

 present in a single individual is small, varying from one to 



Axial filament 



Fia:. 8 



Contractile cytoplasmic sheath 



Diagrams of fiagella. a, flagellum of Euglena (After Biitschli); b, 

 optical longitudinal; and c, transverse section of flagellum of Tra- 

 chelomonas (After Plenge). 



eight. In Hypermastigida there are numerous fiagella (Fig. 12) . 

 Instead of being composed of a homogeneous substance, a 

 flagellum appears to be made up of at least two parts (Fig. 8). 

 An axial filament which is highly elastic, takes its origin directly, 

 or indirectly through the basal granule, in the blepharoplast. 

 Surrounding this filament there is a sheath of contractile cyto- 

 plasm which varies in thickness alternately on either side. 

 The flagellum ordinarily tapers toward the free end. 



