PERIODIC REORGANIZATION IN PARAMAECIUM 493 



Following the definition of Winkler ('08, p. 303), partheno- 

 genesis may be considered as the " apomiktische Entstehung eines 

 Sporophyten aus einem Ei," it being of minor importance whether 

 the reduced or unreduced number of chromosome is present. 

 Strasburger ('07, p. 170) on the other hand puts the greatest 

 weight on the chromosome number and applies the term par- 

 thenogenesis only to cases in which an egg with the haploid 

 number of chromosomes undergoes Entwicklungserregung. Ac- 

 cording to the view of Strasburger, the reorganization process 

 in Paramaecium cannot be termed parthenogenesis. In endo- 

 mixis there is no evidence of a chromosome reduction. This race 

 has existed normally without apparent change for over seven 

 years, during which time it has undoubtedly undergone endomixis 

 nearly one hundred times and thus it is clear that a chromatin 

 reduction, involving a loss of specific chromatin or chromosomes 

 and therefore according to the prevailing view a loss of hereditary 

 units or gene material, cannot have occurred in endomixis. Fur- 

 ther, the nuclear material from which the new nuclear apparatus 

 arises in endomixis cannot be considered as a gamete, because the 

 third micronuclear division which forms the two gametes in Para- 

 maecium aurelia does not occur in endomixis. The eight ' ' reduc- 

 tion" micronuclei are comparable to gametocytes, the paramae- 

 cium individual being a gamont before it starts to form the eight 

 so-called reduction micronuclei (Liihe, Hartmann). So accord- 

 ing to the definition of Winkler it seems impossible to consider 

 endomixis as parthenogenesis in sensu stricto. 



We therefore have employed a new term 'endomixis' for the 

 reorganization process in Paramaecium, in preference to par- 

 thenogenesis which Hertwig applied when he incidentally noted 

 some isolated stages of the nuclear phenomena which we have 

 elucidated. The stages observed by Hertwig were insufficient 

 to give a clue to the sequence of cytological changes — this being 

 necessary for a realization of the importance and proper classi- 

 fication of the reorganization process. 



If subsequent research should show (which from our work 

 seems highly improbable) that a third micronuclear division, 

 involving a chromosome reduction, does occur in the descending 



