638 FERTILIZATION 



disappears. The large granular ball thus formed condenses somewhat 

 and then elongates, starts bending into its normal C-shape, and com- 

 bines with one or two sizeable remnants of the old macronucleus which 

 have persisted through the process. When the elongating macronuclear 

 Anlage approaches the remnants of the old macronucleus, the latter lose 

 their pycnotic appearance and the chromatin reorganizes itself into dis- 

 crete, dispersed granules, again resembling the normal condition. The 

 new and the old portions then unite, end to end, to produce the C-shaped 

 nucleus of the trophic form, the reconstituted portion forming the pos- 

 terior portion. Examination of hundreds of exconjugants at this stage 

 convinces one that the proximity of the elongating Anlage is the influ- 

 ence which brings about the reorganization of the old remnants. The 

 old chromatin is so thoroughly reorganized before joining the new 

 Anlage that it possibly has little more effect on the nature of the 

 new nucleus than if it had been dissolved and re-formed within the new 

 nuclear membrane. 



Ikeda and Ozaki (1918) first reported fragments of the old macro- 

 nucleus being incorporated into the developing macronuclear Anlage in 

 Boveria labialis. 



Kidder (1933a, 1933b) has described an interesting phenomenon oc- 

 curring in the macronuclear Anlagen of Kidderia [Conchophth'nius) 

 mytili and in Ancistruma isseli. At each of the two or three exconjugant 

 fissions which separate the seven or eight new macronuclei, all un- 

 separated macronuclei cast out in an orderly manner a sphere of chroma- 

 tin. According to Kidder, this "may represent the sloughing off of the 

 germinal chromatin contained in the amphinucleus, a substance that is 

 superfluous for the further activity of a purely trophic cell element 

 (Reichenow, 1927)." Diller (1928) suggested this as an explanation 

 of a similar occurrence during endomixis in Trichodina. Chromatin ex- 

 trusions from developing macronuclear Anlagen would appear to be 

 even more closely analogous to the Ascaris type of chromatin diminution, 

 as brought out by Boveri, than is the chromatin diminution described 

 by MacDougall in the division of the macronucleus in Chilodonella. 



Until recently the behavior of the macronucleus in conjugation has 

 been given scant attention. The disintegration of the old macronucleus 

 and the differentiation, number, and distribution of new macronuclear 

 Anlagen have been noted, but no great significance has been attached to 



