PERIODIC REORGANIZATION IN PARAMAECIUM 441 



The formation of the eight micronuclei does not begin until 

 the disintegration of the macronucleus is about finished. Figures 

 36 and 37 (pi. 4) illustrate the coincidence of the end of the 

 macronuclear disintegration and the beginning of the multipli- 

 cation of the micronuclei. The animals in figures 35 and 36 

 show the typical form of the macronuclear destruction which 

 takes place in the reorganization process without the formation 

 of 'wurstformige Schlingen'. A slight resemblance to the char- 

 acteristic macronuclear condition during conjugation is given in 

 the isolated paramaecium of the 4087th generation, thus indi- 

 cating that the macronuclear destruction in conjugation and in 

 the reorganization process may sometimes show similar features. 

 The animals shown in figures 36 and 37 possess either three or four 

 'reduction' micronuclei. The identification of these as ^reduc- 

 tion' micronuclei is based upon their position in a homogeneous 

 protoplasmic layer, and the absence of a micronuclear membrane, 

 together with the general morphological structure of the cell 

 and its fate. 



The diagnostic characters of the 'reduction' micronuclei are 

 still more prominent in later stages. Figure 11 (pi. 1) shows a 

 macronucleus partly devoid of chromatin, eight chromatin bodies 

 and three micronuclei. Two of the micronuclei are apparently 

 starting to divide. The anterior micronucleus seems to be in 

 the process of forming another by an unequal distribution of the 

 chromatin inside the membrane. This is the only micronuclear 

 change of this type which we have observed and may well be 

 due to some irregularity. The formation of mitotic spindles with 

 long distinct threads and crescents have not been seen, and 

 apparently exactly the same type of mitosis as described by 

 Hertwig does not occur in the reorganization process. However, 

 figure 31 (pi. 3) illustrates an animal, from a sub-culture of this 

 race in which conjugation was allowed to occur, having division 

 spindles which approximate to a certain degree some of the 

 spindles figured by Hertwig. It is well known that the mor- 

 phology of the mitotic apparatus varies at different phases of 

 cell life, as for example was found to be the case in Amoeba 

 diploidea by Erdmann ('11, p. 336). 



THE JOURNAL OF EXPERIMENrAL ZOOLOGY, VOL. 17, XO. 4 



