76 RHODA ERDMANN AND LORANDE L. WOODRUFF 



IV. COMPARISON OF THE CYTOLOGICAL PHENOMENA OF THE 

 REORGANIZATION PROCESS IN PARAMAECIUM CAUDATUM 

 AND PARAMAECIUM AURELIA 



This short outline of the cytological changes of the reorgani- 

 zation process in Paraniaecium caudatum makes it clear, we 

 believe, that there is no fundamental difference between the 

 morphological features of this process in Paramaecium caudatum 

 and Paramaecium aurelia, further than that incidental to the 

 fact that the former species has one micronucleus and the latter 

 two micronuclei in its typical vegetative stages.^ The destruction 

 of the old macronucleus and the formation of a new macronuclear 

 apparatus of micronuclear origin is effected in both species. 



However, there are some interesting minor variations which 

 it may be well to contrast. The 'reduction' division in the re- 

 organization process of Paramaecium caudatum with its 'dumb- 

 bell' formation resembles more closely the phenomenon in the 

 conjugation of this species than do the features of the 'reduction' 

 micronuclear phenomena in the reorganization process of Para- 

 maecium aurelia resembles those of conjugation in that species. 

 We were unable to discover the same features in the 'reduction' 

 division in Paramaecium aurelia during the reorganization proc- 

 ess that were described by Hertwig for the comparable stages in 

 conjugation. Hertwig ('14) figures a stage (text fig. 2, animal 3) 

 which he interprets, together with the condition in the two pre- 

 vious animals (animals 1 and 2), as " Depressionserscheinungen 

 von Paramaecium aurelia." We would interpret Hertwig's 

 animal 3, on the basis of the animals figured in our earlier paper 

 (fig. 12, pi. 1, etc.) as a cell in a stage of the reorganization proc- 

 ess after the formation of four 'reduction' micronuclei two of 

 which are already preparing for the second 'reduction' division. 

 Animals with this morphological structure will actually complete 

 the reorganization process, as we have proved ('14, III), and 

 therefore such animals as figured by Hertwig cannot be inter- 

 preted as depression stages. Thus Hertwig indirectly and we 



^ For a discussion of the specific characters of Paramaecium aurelia and Para- 

 maecium caudatum and the literature on the subject, cf. Woodruff, Journal of 

 Morphology, vol. 22, p. 223, 1911. 



