472 



BIOLOGY OF THE PROTOZOA 



The above method was first used in connection with the life 

 history of Paramecium caudatum (Calkins, 1904), and many other 

 experiments of similar nature were made on this genus by later 



12 3 45 6789 10 11 12 13141516 17 181920 212223 24 25 26 2728 29303132 3334 353637383940 41 



Fig. 198. — Composite graph of vitality of twenty-three series of Uroleptus mobilis, 

 each having vitaHty of more than 85 per cent (sohd line). The dotted line is the 

 vitality graph of the double organism. (After Calkins.) 



observers. It turned out to be an unfavorable object for the study 

 of this particular problem of vitality, for in 1914 Woodrufl' and 

 Erdmann announced the discovery of a periodic reorganization 

 process in Paramecium aiirelia which is exactly comparable with 



Ficj. 199. — Vitality graph of Plcirrolricha hinccolata. (After Baitsell.) 



one type of parthenogenesis occurring in Metazoa (p. 540). The 

 discovery of this reorganization process which they called "endo- 

 mixis" was the culmination of Woodrutl's brilliant and long-contin- 



