MORPHOLOGY 



59 



Stylonychia, etc., "walk" on frontals, ventrals, and anals, while swim- 

 ming movement by other species is of different types. 



In all euciliates except Holotricha, there are adoral membranellae. 

 A membranella is composed of a double ciliary lamella, fused com- 

 pletely into a plate (Fig. 12, b). A number of these membranellae 

 occur on a margin of the peristome, forming the adoral zone of 



cpg 



Fig. 12. Diagrams of cirrus and membranella of Euplotes eurystomus, 

 X1450 (Taylor), a, anal cirrus in side view; b, a membranella (cpg, co- 

 agulated protoplasmic granules; cr, ciliary root; fp, fiber plate; k, kineto- 

 some) . 



membranellae, which serves for bringing the food particles to the 

 cytostome as well as for locomotion. The frontal portion of the zone, 

 the so-called frontal membrane appears to serve for locomotion and 

 Kahl considers that it is probably made up of three lamellae. The oral 

 membranes which are often found in Holotricha and Heterotricha, 

 are transparent thin membranous structures composed of one or two 

 rows of cilia, which are more or less strongly fused. The membranes, 

 located in the lower end of the peristome, are sometimes called 

 perioral membranes, and those in the cytopharynx, undulating mem- 

 branes. 



In Suctoria, cilia are present only during the developmental 

 stages, and, as the organisms become mature, tentacles develop in 

 their stead. The tentacles are concerned with food-capturing, and 



