648 



ENDOMIXIS 



tinued well-being of the race, but provisions are also made for the 

 periodic destruction of the macronucleus and its replacement from the 

 micronuclear reserve: in some species by endomixis and autogamy, and 

 probably in all by conjugation. 



Endomictic Phenomena 



A periodic replacement of the macronuclear apparatus, without syn- 

 karyon formation, was described in Paramecium aurelia, and named en- 



A 

 B 

 C 



O 

 E 

 F 

 G 

 H 



1 



J 



Figure 155. General plan of the usual nuclear changes during endomixis in Para- 

 mecium aurelia. A, typical nuclear condition; B, degeneration of macronucleus (chro- 

 matin bodies not shown) and first division of micronuclei; C, "climax": second division 

 of micronuclei ; D, degeneration of six of the eight micronuclei ; E, division of the 

 cell; F, first reconstruction micronuclear division; G, second reconstruction micro- 

 nuclear division; H, transformation of two micronuclei into macronuclei; I, micro- 

 nuclear and cell division; J, typical nuclear condition restored. (Constructed from the 

 description and figures of Woodruff and Erdmann, 1914.) 



domixis, by Woodruff and Erdmann (1914). Following their account, 

 in summary, endomixis in this species involves the resolution of the old 

 macronucleus into chromatin bodies, which disintegrate in the cytoplasm. 



