50 



PROTOZOOLOGY 



The membranes, located in the lower end of the peristome, are 

 sometimes called perioral membranes, and those in the cyto- 

 pharynx, undulating membranes. 



In Suctoria, cilia are present only during the developmental 

 stages, and, as the organisms become mature, tentacles are de- 

 veloped. The tentacles are concerned with food-capturing, and 

 are either prehensile or usually suctorial. In a few instances the 



cpg 



Fig. 12. Diagrams of cirrus and membranella of Euplotes pateUoi 

 X1450 (Taylor), a, an anal cirrus in side view; b, a membranella; bg- 

 basal granule; cpg, coagulated protoplasmic granules; cr, ciliary root; 

 fp, fiber plate. 



tentacles are tubular and this type is interpreted by Collin as 

 possibly derived from a cytostome and cytopharynx of the ciliate 

 (Fig. 13). 



Although the vast majority of Protozoa possess only one of the 

 three organellae of locomotion mentioned above, a few may 

 possess pseudopodia in one phase and fiagella in another phase 

 during their life-cycle. Among many examples, may be men- 

 tioned Dimastigamoebidae (Fig. 139), Tetramitus rostratus (Fig. 

 122), etc. Furthermore, there are some protozoans which possess 

 two types of organellae at the same time. Flagellum or fiagella 



