PERIODIC REORGANIZATION IN PARAMAECIUM 455 



generation and the involution of the chromatin bodies was com- 

 pleted in the 4316th generation. Of the eight cells which were 

 formed by the three following divisions (4313 to 4316), four in 

 the 4316th generation were without chromatin bodies. The pre- 

 ceding figure (fig. 26, pi. 3) represents an animal from Line VI, 

 4185th generation. Two divisions have occurred since the climax 

 at the 4183d generation. Here the chromatin bodies which still 

 remain have not lost their original shape, but if one considers 

 the four division products which result from the divisions 4183 

 to 4185 then it is evident that a second method of decreasing 

 the number of chromatin bodies is by their distribution to the 

 daughter cells. As an example of this distribution the following 

 case may be cited (cf . text fig. 8 for sister line) : 



Line VI 4183d generation has 19 chromatin bodies 

 Line VI 4185th generation, animal a has 6 chromatin bodies 

 •iLine VI 4185th generation, animal b has 5 chromatin bodies- 

 Line VI 4185th generation, animal c was not observed 

 Line VI 4185th generation, animal d was kept alive to continue the line 



Two further divisions took place in twenty-four hours: 



Line VI 4187th generation, animal a has still 3 chromatin bodies (fig. 29, pi. 3) 

 Line VI 4192d generation has 1 chromatin body 



Therefore the ascending phase of the process can be followed 

 in nine generations; that is, from the 4183d generation, which 

 is at the end of the climax, to the 4192d generation which is a 

 typical vegetative paramaecium cell except that one chromatin 

 body still persists. Since the beginning of the process was ob- 

 served at the 4182d generation, it is evident that the nuclear 

 changes in this case extended over ten generations. The typical 

 reduction of the division rate at the climax of the process to 

 one division in approximately thirty-six hours occurred in this 

 case at the 4182d to 4183d generation, and the increase in the 

 rate to three divisions in twenty-four hours which characterizes 

 the ascending phase of the process occurred at the 4189th 

 to 4192d generation. 



When the second or third division after the formation of the 

 macronuclear anlagen has occurred the new macronucleus has 



