220 



Fig. 7ü. The defecation and excretion by a vacuole situated in the canal 

 wall. The small circles represent green «symbiotic" algae. Mag- 

 nif. ± 400 times. See p. 163—164. 



Fig. 77. The protruding and withdrawing of a defecation (and excretion) 

 vacuole at several canals; in 1. a vacuole has not yet been formed ; 

 in 4. it finally protrudes into the 3"^ canal and bui'sts. Tlie small 

 circles represent green „symbiotic" algae. Magnif. rb 400 times. 

 See p. ie::;— 166. 



