490 LORANDE LOSS WOODRUFF AND RH. ERDMANN 



It has been shown in the main pedigreed culture of Para- 

 maecium aurelia that at intervals throughout the seven years 

 (to date) of its existence the process has occurred. It has also 

 been shown that when a mass culture of animals from this race 

 was under just the proper conditions, typical conjugation oc- 

 curred. Thus it is proved that both the reorganization process 

 and conjugation are potentialities of the animals of the same race — 

 and therefore there is no evidence for the view of Calkins ('13) 

 that conjugating and non-conjugating races of Paramaecium exist 

 (cf. p. 429), or that ''apparently some paramaecia are potential 

 germ cells, others are not." The cell clearly has two methods 

 of reorganization which, so far as the evidence at hand indicates, 

 may be employed indiscriminately. One is conjugation, the 

 other is the reorganization process. 



The chief morphological changes incident to conjugation and 

 the process may be contrasted as follows: 



In each case the old macronucleus is dissolved in the cytoplasm 

 and micronuclear reduplication occurs until eight are present 

 in the cell; 



In conjugation one of these micronuclei persists and by an 

 extra division forms the stationary and migratory nucleus. This 

 division is directly prepara,tory for the accession of foreign chro- 

 matin. After the mutual interchange of the reduced micronuclei 

 is effected, a syncaryon is formed. The latter gives rise to the 

 new nuclear apparatus ; 



In the reorganization process, on the other hand, one or two 

 micronuclei persist (cf. p. 446), from which the new nuclear 

 apparatus arises. 



After co7ijugation the reorganized cell has a new macronuclear 

 and micronuclear apparatus composed of combined material from 

 the two conjugants; 



, After the reorganization process the reorganized cell has a new 

 macronuclear and micronuclear apparatus composed of material 

 from its own micronuclei. 



In a word — the essential morphological difference is the entire 

 absence of the introduction of foreign nuclear {and cytoplasmic) 

 Tnaterial into the cell during the reorganization process. 



