REPRODUCTION 



201 



amount of cytoplasm behind in the shrunken pellicle of the smaller 

 conjugant which then separates from the other (j). In the larger 

 exconjugant, two pronuclei fuse, and the other two degenerate and 

 disappear (g, h) . The synkaryon divides into two nuclei, one of which 

 condenses into the micronucleus and the other grows into the macro- 

 nucleus (i, k-m). This is followed by the loss of cilia and encystment. 

 While ordinarily two individuals participate in conjugation, three 



Fig. 87. Conjugation of Metopus es (Noland). a, early stage; b, first 

 micronuclear division; c, d, second micronuclear division; e, third micro- 

 nuclear division; f, migration of pronuclei from one conjugant into the 

 other; g, large conjugant with two pronuclei ready to fuse; h, large con- 

 jugant with the synkaryon, degenerating pronuclei and macronucleus; 

 i, large exconjugant with newlj r formed micronucleus and macronucleus 

 j, small exconjugant with degenerating macronucleus; k-m, development 

 of two nuclei, a, X290; b-j, X250, k-m, X590. 



