186 



REPRESENTATIVE SINGLE-CELLED ANIMALS 



new contractile vacuole is formed for each " daughter," and new 

 gullets arise in each from the material of the original buccal region. 

 After separation, the daughter cells normally grow to full size 

 before a new division occurs. Under favorable conditions there 



A. Two individuals unite by 

 buccal grooves. The micrO' 

 nuclei separate from the 

 macronuclei. 



B. The macronucle'us begins to 

 degenerate. The micTonucleus 

 divides. 



C. The micronuclei divide 

 again. Three of each four 

 disappear. 



D. The remaining micronuclei 

 divide to form migratory and 

 stationary nuclei. Exchange 

 of migratory nuclei. 



f. The migratory and stationary 

 nuclei unite. 



r. The fusion nucleus Is 

 thus formed. 



0. The individuals separate. 



H. Division of the fusion nucleus. 



I. Division, as shown. 



J. Differentiation into macro- and 

 micronuclei occurs and dis- 

 appearance of three micronuclei 



K. Cells and nuclei 

 divide as shown to 

 produce the original 

 condition. 



Fig. 100.— Schematic representation of conjugation in Paramoccium caudatmn. 

 (Redrawn from Jennings, "Life and Death, Heredity and Evolution in Unicellular 

 Organisms," copyright, 1920, Richard G. Badger, printed by permission.) 



