%; 



Fig. 1 Uroleptus mobilis. Normal individual and individuals degenerated 

 through old age. Camera drawings, same magnification. 



1 Normal individual with typical nuclear complex of eight macronuclei and 

 four micronuclei. 



2 Individual from the F series in the 315th generation. Four micronuclei 

 still present, but greatly reduced. The macronuclei have undergone granular 

 degeneration. The F series died out in the 317th generation. 



3 A prematurely degenerated individual from the C series in the 316th gen- 

 eration. The micronuclei have entirely disappeared. The macronuclei show 

 the characteristic granular degeneration. The C series died out in the 348th 

 generation. 



4 Individual from the A series in the 313th generation (a sister cell of the 

 last individual of the series). All of the nuclei have degenerated, the macro- 

 nuclei by granule formation, the two remaining micronuclei by hypertrophy. 



142 



