454 



GARY N. CALKINS 



maturation division at the time when cut. The experimental 

 individual regenerated within a few hours, but required nine 

 days for reorganization and the first division (fig. 3). It divided 

 on the average 14.6 times per ten days for the first sixty days 

 of life, while the parent P series divided 14.2 times per ten days 

 during the same calendar period, indicating, like the PXl series, 

 a very slight rejuvenescence. That there was rejuvenescence, 

 however, is shown by the fact that the division rate of the P 



?X€ 



/l3 /# 



7>X7 



^ 



M 



Fig. 3 PX6 series. Sketches from the living animal on successive days 

 during reorganization after cutting. 



Fig. 4 PX7 series. Sketches of the living animal during reorganization. 



series from the start of the filial series up to the time of its last 

 division was 8.5 divisions per ten days while the rate for the 

 filial PX6 series during the same period was 11.4 divisions. The 

 filial series lived and divided for 160 days after the parent series 

 had died a natural death, and finally died at the age of 376 

 days and 313 generations. It was more vigorous, therefore, 

 than the companion series derived from a cut individual (PXl 

 series), a vigor also shown by its relative vitality of 81.3 per cent, 

 but was less vigorous than the common parent P series and less 

 vigorous than the normal control PV series. 



