126 GARY N. CALKINS 



Also, the fact should be emphasized again, that throughout 

 the entire history of the protoplasm, with the exception of a few 

 weeks at the outset, the same standardized culture medium, 

 made fresh each day, has been used. Waning vitality cannot 

 be attributed to deleterious food conditions, for, on the same day 

 with the same food, one portion of the protoplasm may be at the 

 lowest ebb of vitality, while other portions are in the full 

 swing of metabolic vigor, all portions being equally old in 

 point of time. The difference in vigor between them cannot be 

 due, therefore, to environmental or external conditions, but must 

 be attributed to the internal conditions following conjugation. 



This protoplasm has been studied in fourteen different series 

 as follows: The A series, or parent race, started as an ex-conju- 

 gant from a pair of 'wild' Uroleptus mobilis on November 16, 



1917, and died on September 18, 1918, in the 313th generation. 

 The C series, or first filial series (Fi) , started on February 4, 1918, as 

 an ex-con jugant from a pair of individuals in approximately the 

 78th generation of the A series. It died out on December 30, 



1918, in the 348th generation. The D series, or second filial 

 series, started as an ex-conjugant on March 9, 1918, from the A 

 series in the 137th generation and died out on October 13th in 

 the 271st generation. An E series was also started at the same 

 time from the same source, but was discarded after the 50th 

 generation. The F series, or first F2 series, started as an ex- 

 conjugant on March 25, 1918, from the C series in the 86th 

 generation (the grandparent A series was ill the 155th genera- 

 tion). This series died Decern !>er 21, 1918, in the 317th gener- 

 ation. The H series, or third l'\ series, started as an ex-conju- 

 gant on April 24, 1918, from the A series in the 237th generation, 

 and died out on January 16, 1919, in the 277th generation. The 

 I series, or first F3 series, started as an ex-conjugant on July 7, 

 1918, from the F series in the 143rd generation (the Fi grand- 

 parent C series was in the 224th generation and the great-grand- 

 parent A series was in the 278th generation) . This series is still 

 living in the 321st generation, but has stopped dividing and will 

 die shortly. The J series, or fourth Fi series, started as an ex- 

 conjugant on August 20, 1918, from the A series in the 311th 



