CHAPTER XXX 



CILIOPHORA 



Paramsecium Caudatum. — This is the most common infusor- 

 ian met with in stagnant water. Its 

 length varies from 120 to 325/i. The 

 cell is spindle-shaped with a deep oral 

 groove which takes a spiral course on 

 one side of the body. The surface is 

 thickly set with active cilia. Food 

 particles are swept into the oral 

 groove, enter the cytoplasm at its 

 bottom and circulate in the cell within, 

 food vacuoles. Near the center of the 

 cell is a large macronucleus and near it 

 a smaller micronucleus. Multiplication 

 takes place by simple longitudinal or 

 oblique division. 



Conjugation is isogamic. The sim- 

 ilar conjugating cells ad^iere to each 

 other, the micronuclei divide twice and 

 three of the four nuclei thus produced 

 disintegrate, as does also the macro- 

 nucleus. The remaining micronucleus 

 divides into two and one of these 

 passes into the other conjugating cell 

 in exchange for a similar element. 

 The newly acquired element unites 

 with the element which remained be- 

 NK micronucleus; c, gullet; hind to form the uew nuclcus. The 



N, food vacuoles; CV, contrac- 

 tile vacuoles. {After Doftein.) new nucleus divides three times in suc- 



452 



Fig. 216. — P ar amacium 

 caudatum. K, Macronucleus; 



