Flo. 185. Paramecium caudatum: semi-diagrammatic figure to show the structure. 

 P., peristomial groove ; o, mouth ; oes., oesophagus, containing an undulating 

 membrane (t/.m.) ; f.v.', food-vacuole forming at the base of the oasophagus ; 

 f.v.,f.v., other food-vacuoles circulating in the endoplasm ; c.v., c.v., the two 

 contractile vacuoles, showing a different condition in each, the upper one full 

 and ready to empty itself, the lower one beginning to fill after a contraction ; 

 ex., excretory crystals in the endoplasm ; N, macronucleus ; n,. micro nucleus ; 

 tm. f triohocysts ; al., alveolar layer; p., pellicle. After Lang (10), slightly 

 modified. 



