. r/r 



FIG. 18. Paramcecium caudatum. A, the living animal from the ventral aspect ; 

 B, the same in optical section : the arrow shows the course taken by food- 

 particles ; C, a specimen which has discharged its trichocysts ; D, diagram of 

 binary fision ; buc. gr. buccal groove ; co) t. cortex ; en. cuticle ; c. vac. con- 

 tractile vacuole ; f.vac. food vacuole ; gul. gullet ; med. medulla ; nn. meganu- 

 cleus ; pa. nn. micronucleus ; trch. trichocysts. (From Parker's Biology ) 



