STR UCT URAL DIFFERENTIA TIONS 



151 



ellipsoidal, quadrilateral or irregular, and always have a basal plate 

 made up of the basal granules of the fused cilia. Under unfavorable 

 conditions of the medium in which the organisms live, and usually 

 after imperfect fixation, the constituent cilia become separated 

 particularly near the tip, and the cirri then present a most frayed- 



''MC';- 



Fig. 79. — Types of hypotrichous ciliates. A, Peritromus emynoe; B, Kerona pedi- 

 cuhis; C, Diophrys appendiculatus; D, Euplotes charon. {A, C, D, after Calkins; B, 

 after Stein.) 



out or ragged appearance. They vary in size from extremely minute 

 cilia-like marginal cirri to great ventral brushes in forms like Ony- 

 chaspis (Fig. 80) or huge hooked structures as in Uronychia and 

 other Euplotidse (Fig. 79). 



Cirri are preeminently organs of locomotion, but, unlike other 



