author's abstract of this paper issued 

 by the bibliographic service, october 17 



MICRONUCLEATE AND AMICRONUCLEATE RACES OF 



INFUSORIA 



LORANDE LOSS WOODRUFF 

 Oshorn Zoological Laboratory, Yale University 



FOUR FIGURES 



The dimorphic condition of the nuclear apparatus of the Infu- 

 soria is one of the most interesting speciahzations exhibited by 

 the group, representing, as is well-known, a segregation of 

 the so-called 'somatic' or trophochromatin from the 'generative' 

 or idiochromatin into distinct bodies, the macronucleus and 

 micronucleus. It has generally been accepted that this differen- 

 tiation of the nucleus is a diagnostic character of the Infusoria, 

 and, aside from parasitic or aberrant species, the only apparent 

 exceptions have revealed the micronuclei as distinct bodies 

 within the macronuclear membrane during vegetative stages, 

 or emerging as such at the onset of conjugation. 



It is true that there are many ciliates in which the micronu- 

 cleus has not been observed, but naturally such cases are attrib- 

 uted rather to the difficulties sometimes involved in determining 

 these bodies than to their absence. This conclusion has been 

 strengthened by the fact that in micronucleate forms the removal 

 of the micronucleus through degeneration or by experimental 

 means has proved to be the death warrant of the cell. All the 

 evidence indicates that once the chromatin differentiation is 

 established during conjugation or endomixis, the die is cast so 

 far as the macronucleus is concerned. It is destined to play its 

 part during the vegetative life of the cell and to be replaced from 

 the micronuclear complex at the next conjugation or endomixis 

 period. 



329 



