436 LORANDE LOSS WOODRUFF AND RH. ERDMANN 



In addition to this material preserved daily from Sub-culture 

 IE, we had at our disposal, as already mentioned, preparations 

 preserved at various periods throughout the life of the main 

 culture (I). These had been fixed in a saturated solution of 

 corrosive sublimate with 5 per cent glacial acetic acid, stained 

 with Ranvier's picrocarmine and mounted in damar. 



III. DESCRIPTION OF THE CYTOLOGICAL CHANGES IN THE 

 REORGANIZATION PROCESS 



The general outline of this remarkable cytological process which 

 accompanies the rhythms clearly shows that a complete internal 

 reorganization of the Paramaecium cell occurs without cell fusion. 

 The details to be presented were obtained as already described 

 from Sub-culture IE, from October 27, 1913, to April 27, 1914, 

 and certain stages were substantiated with specimens which had 

 been preserved from the main culture (I) at various isolated 

 periods during the previous six and one-half years o'f its existence. 

 Figure 1 (pi. 1) shows a typical specimen of Paramaecium aurelia 

 isolated from the main culture (I) on April 11, 1908, at the 424th 

 generation, i.e., 3596 generations before Sub-culture IE was 

 started. Figure 2 (pi, 1) represents an animal in the 4020th 

 generation at the time Sub-culture IE was branched from the 

 main Culture I. 



The reorganization process resolves .itself naturally into three 

 periods: the descending phase, the climax, and the ascending 

 phase. 



A. DESCENDING PHASE 



The macronucleus of a typical Paramaecium aurelia, which 

 is not undergoing the reorganization process, consists of fine 

 chromatic granules enclosed within a relatively thick membrane. 

 The finer structure has been fully described by Maupas ('89, 

 p. 217) and Hertwig ('89, p. 9). The two micronuclei, in a simi- 

 lar period with respect to the process and in the resting stage 

 between two cell divisions, are more or less compact and homo- 

 geneous, and often lying in a pair near the macronucleus which 

 sometimes obscures them from view. The cvtoplasm of the cell 



