144 GARY N. CALKINS 



series, the only possible explanation of the restoration of vitality 

 in filial series lies in the process of conjugation by which such 

 filial series are started. 



Although table 4 shows that all ex-con jugants have practically 

 the same optimum division rate at corresponding periods of the 

 life cycle, it does not show the actual differences in metabolic 

 activity between parent and filial series ,in identical calendar 

 periods. If conjugation does not restore vitality, the division 

 rate of a filial series should not differ from the division rate of 

 the parent series from which it has been derived; on the other 

 hand, if it does restore vitality, the extent to which it is restored 

 will be indicated by the difference in the average division rates 

 of parental and filial series in identical calendar periods. 



These differences in average division rates of parent and off- 

 spring series are clearly shown in table 5. Here two interesting 

 phenomena are evident: first, reading across, the table shows that 

 the discrepancy between parent and offspring increases with the 

 age of the parent series at the time of conjugation; second, 

 reading down, it shows that, while both series are losing vitality, 

 the parent series is losing it more rapidly than the filial series. 



In regard to the first of these phenomena, it will be noted that 

 the C series came from the A series when the latter was in the 

 78th generation and that, during the first sixty days of the filial 

 series, the protoplasm of each line had the power to divide 1.53 

 times more in ten days than that of each line of the parent A 

 series in the same period. The D series came from the A series 

 when the latter was in the 137th generation, that is approxi- 

 mately fifty generations older than the protoplasm which gave 

 rise to the C series. The discrepancy now between the parent 

 series A and the filial series D amounted to 3.03 divisions in ten 

 days during the first sixty days of the D series. That is the 

 protoplasm of each line of the offspring series had the power to 

 divide 3.03 times more in ten days than that of each line of the 

 parent A series. The filial H series came from the same parent 

 A series when the latter was in the 237th generation, or about 

 150 generations older than when the C series was formed. The 

 discrepancy between parent A and offspring H series now 



