NONCHROMOSOMAL GENES 



Autogamy 



FIGURE 9.10. Autogamy and conjugation 

 in Paramecium. 



1 . Animals with one macronucleus and two 

 micronuciei per cell. 



2. Each micronucleus undergoes meiosis. 

 Result: eight haploid nuclei. The macro- 

 nucleus begins to degenerate. 



3". Seven of the nuclei degenerate, and the 

 eighth wilt divide. 



4. In conjugating animals, one member of 

 each pair of remaining nuclei is exchanged. 



5. The haploid nuclei fuse to form the new 

 diploid micronucleus, which divides twice, 

 giving rise to two new macronuclei and two 

 micronuciei. 



6. At the next cell division, one macro- 

 nucleus goes to each daughter cell, but the 

 micronuciei divide again so that two are 

 present in each cell. 



ment from each parent. Each fusion nucleus divides twice, producing 

 four diploid nuclei, two of which remain as micronuciei, and two of 

 which enlarge, becoming the new macronuclei. The micronuciei divide 

 once more so that upon cell division each daughter has one macronucleus 

 and two micronuciei. 



