DERIVED ORGANIZATION— TAXONOMIC STRUCTURES 171 



In Campanella umbellata such a reservoir is replaced by two definitely 

 walled evacuation canals, while in Pycnothri.v the excretory canal 

 is said to be provided with special cilia. 



c. v. 



Fig. 95. — Golgi bodies in Chilomonas Paramecium (B) and Paramecium cau- 

 datum (A and C). c.v., Contractile vacuole; r, radial canals of Paramecium. (After 

 Nassonov.) 



In some types of parasitic ciliates (Biitschliidae and Paraiso- 

 trichidae) a peculiar type of "concrement vacuole" has been de- 

 scribed by Dogiel (1929) which appears to be a normal part of the 

 derived organization. These are interpreted, not as excretory, 

 but as special structures with a statolith function. 



