72 ORGANISMS OF ONE CELL 



process of protoplasmic reorganization followed by renewal or 

 re-birth of all vital activities including that of reproduction. 



Investigations subsequent to those of Blitschli have revealed 

 all the happenings during the process of conjugation in Para- 

 mecium. The micronuclei in each cell first begin to swell by 

 the absorption of fluids from the endoplasm; the chromatin 

 increases enormously in quantity and becomes drawn out in 

 the form of rods termed chromosomes, too numerous to count. 

 Each of these chromosomes is then divided into two equal parts, 

 after which the micronuclei divide through the center, each 

 daughter micronucleus receiving one-half the original chroma- 

 tin. There are now two micronuclei in each cell and all four 

 divide once again, forming eight in all or four in each cell. Of 

 these four, three degenerate and are absorbed in the endoplasm 

 leaving one micronucleus in each cell. These then divide once 

 again forming what are called pronuclei one of which migrates 

 from its cell into the other cell so that a mutual exchange of 

 pronuclei takes place. Each wandering pronucleus unites 

 with the stationary pronucleus of the opposite cell and fuses 

 completely with it forming a fertilization nucleus (Fig. 30, A-H). 



In the meantime the macronucleus of each cell begins to 

 break into pieces and to degenerate and sooner or later it en- 

 tirely disappears, although this final disappearance does not 

 occur until some time after the two cells separate and divisions 

 have begun. After separation of the conjugating cells the fer- 

 tilization nucleus divides three consecutive times thus forming 

 eight micronuclei. Four of these begin to swell, change in 

 character and develop into four new macronuclei. After 

 twenty-four to forty-eight hours the exconjugant divides. 

 Two macronuclei and two micronuclei going into each daughter 

 cell, and after another twenty-four hours these cells divide 

 again one micronucleus and one macronucleus going to each 

 daughter cell. With this final division the normal relations 

 of the cell are reorganized and the processes of conjugation 

 are ended the resulting cells having each one macronucleus and 

 one micronucleus (Fig. 30, I-P). 



With the breaking up of the old macronucleus the protoplasm 



