PROTOZOA 



15 



alleged, by alterations in the surface tension of the protoplasm, and 

 it is probable that the movement {amoeboid movement) in the course 

 of which they are formed is not fundamentally different from the 

 movements of muscles, or cilia, or flagella. Granules may often be 

 seen to stream up and down the axopodia and rhizopodia. Flagella 

 are lashes, long and usually few in number, which by a rowing 

 (Fig. 10) or by an undulating motion (Fig. 11) draw or propel the 

 body or attract particles to it. In the rowing stroke the flagellum is 



^,^r«rjn. 



-^h'. 



-nuc. 



Fig. 8. 



Fig. 9. 



Fig. 8. Clathritlina. A, Ordinary individual, x 200. B, Binary fission within 

 the lattice. C, Escaped fiagellate individual. After Leidy. 



Fig. 9. Part of a longitudinal section through a Paramecium showing the 

 trichocysts at the end of the body discharged, and in the endoplasm material 

 for the replacement of trichocysts. From Saunders, after Mitrophanov. 

 71UC. meganucleus; tr. undischarged trichocysts; tr.' discharged trichocysts; 

 tr.m. material for replacing trichocysts. 



held rigid and slightly concave in the direction of the stroke; in 

 recovering its position it bends as it is drawn back, so that less 

 resistance is offered to the medium. When, as is usually the case, the 

 flagellum beats obliquely, or the undulations pass around as well as 

 along it, the body rotates as it advances, or if it be fixed a whirlpool 

 is set up. Down each flagellum runs an internal thread, the axial 

 filament^ which, on entering the body or at some distance within it, 

 joins a basal granule.^ The latter is in most cases connected to the 



^ This structure is sometimes called the blepharoplast, but as that name has 

 also been applied to parabasal bodies its use is best avoided. 



