458 LORANDE LOSS WOODRUFF AND RH. ERDMANN 



was little chance for error for their cytological phenomena fre- 

 quently overlapped. 



As has already been indicated, it is obviously impossible to 

 study every animal every day and so have a complete picture 

 of the animals of a single line at any one time, since one cell 

 must be maintained if the line is to be kept alive. In certain 

 cases it was deemed best to keep more than one animal alive in 

 order to further safeguard the life of the line because death some- 

 times occurs during the process. However, it has been possible 

 actually to determine the entire sequence of events by preserving 

 all of the animals of certain lines at selected periods in the pro- 

 cess. The fact that the process occurred nearly synchronously 

 in the various lines and at comparatively regular intervals ren- 

 dered this procedure particularly valuable. 



A. SERIES OF CELLS FROM LINE ^'I AND ITS DERIVATIVES 



Line VI at the 4057th generation afforded the first proof of 

 the reconstruction of the cell, two characteristic macronuclear 

 anlagen and twenty-four chromatin bodies being present. The 

 animal is in the beginning of the ascending phase of the process. 

 In the 4060th generation the process was completed as the ani- 

 mal does not show any macronuclear remnants. The large num- 

 ber of typical animals which followed in this line for nearly fifty 

 divisions was finally interrupted by the appearance of a cell at 

 the 4094th generation which has two chromatin bodies. Its 

 sister cell (40942) has no signs of the beginning of the process 

 and the following generations up to the 4102d generation showed 

 no further traces of reorganization. This indicates that the cells 

 when the critical period is approaching may start the process 

 but not carry it to completion. The total reconstruction of 

 the nuclear apparatus took place between the 4100th and 4107th 

 generation. Text figure 4 gives two stages of the process; the 

 disintegration of the old macronucleus in Ai and A2 and A3 and 

 the formation of the new macronuclear anlagen in A4. In the 

 4100th and the 4102d generation the macronucleus is merely 

 eliminating chromatin bodies while in the 4103d generation the 



