140 



MANUAL OF ELEMENTARY ZOOLOGY 



Internal 

 Organs. 



A meganucleus and a micronucleus are present, the former 

 a long, curved band, the latter small and placed 

 beside the meganucleus, usually in the upper part 

 of the body. There is a contractile vacuole, 

 which has no canals. It lies in the upper region of the body 

 and communicates with the vestibule through a reservoir, 

 which has a narrow permanent opening. The contractile 



cm,-0 



Fig. 86. — Vorticella, highly magnified. 



an., Position of temporary anus ; c.f., contractile 

 filament ; c.v., contractile vacuole ; cut.st., 

 cuticle of the stalk ; dsc, disc ; cc. , ectoplasm ; 

 /.v., food vacuoles ; g., gullet ; i.ci., inner 

 row of cilia; meg., meganucleus; mi., micro- 

 nucleus ; myn., myonemes ; o.ci., outerrow 

 of cilia ; pst., peristome ; res., reservoir of 

 contractile vacuole; rim ; u.m., undulating 

 membrane ; v., vestibule. 



vacuole contracts sharply at intervals, discharging into the 

 reservoir. The latter then contracts slowly, driving its 

 contents into the vestibule, but not itself disappearing. 

 Feeding and digestion take place much as in Paramecium. 

 The little organisms which serve as food are collected and 

 driven into the gullet by the action of the cilia. The food 

 vacuoles follow a definite, winding course in the body, passing 

 through stages similar to those in Paramecium. The faeces 



