ORIGIN OF THE INDIVIDUAL 



245 



B 



1) 



G 



FIG. 130. Diagram of the nuclear changes during conjugation in Paramecium 

 aurelia. A, union of two individuals along the peristomal region; B, degeneration of 

 rnacronucleus and first division of the micronuclei; C, second division of micronuclei; 

 D, seven of the eight micronuclei in each conjugant degenerate (indicated by circles) 

 and disappear; E, each conjugant with a single remaining micronucleus; F, this nucleus 

 divides into a stationary micronucleus and a migratory micronucleus the gametic 

 or pronuclei. The migratory micronuclei are exchanged by the conjugants and fuse 

 with the respective stationary micronuclei to form the synkarya. This is fertilization. 

 G, conjugants, with synkarya, separate (only one is followed from this point); //, first 

 division of synkaryon to form two micronuclei; I, second reconstruction division; 

 /, transformation of two micronuclei into macronuclei; K. division of micronuclei ac- 

 companied by cell division; L, typical nuclear condition restored. 



