220 



Fig. 76. 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 i. a vacuole has not yet been formed; 

 in 4. it finally protrudes into the 3"i canal and bursts. The small 

 circles ^represent green „symbiotic" algae. Magnif. ± 400 times. 

 See p. 163—166. 



