SURVEY OF INVERTEBRATES 45 



der strictly anaerobic conditions for several liours. 

 Eventually, however, the animals became motionless, but 

 they recovered if oxygen was readmitted. The time re- 

 quired for recovery depended upon the duration of the 

 preceding anaerobic period. Variations in sensitivity 

 towards lack of oxygen seem to occur in ditferent spe- 

 cies. Flahellula, for instance, became motionless in a 

 very short time and the activity of its digestive vacu- 

 oles ceased rapidly (this phenomenon, too, was reversi- 

 ble). On the contrary, the ability of Pelomyxa to live an- 

 aerobically is quite pronounced. Lindeman (1942) found 

 that this organism survived for at least 60 days in anaero- 

 bic cultures. 



Eegarding other free-living rhizopods only a few data, 

 obtained by Harvey (1926) in his experiments with radio- 

 larians, are available. He reports that Thalassicola and 

 Colozoun can be kept for 45 minutes under strictly anaero- 

 bic conditions and that these organisms will still lumin- 

 esce whenever the culture is shaken. 



(c)Ciliates. A considerable number of experi- 

 ments (Table 9) were made with a variety of ciliates, 

 like Paramaecium, Colpoda, VorUcella, etc., which, under 

 ordinary circumstances, lead a clearly aerobic life (Loeb 

 and Hardesty, 1895 ; Putter, 1905 ; Lohner, 1913 ; Fortner, 

 1924; Kalmus, 1928; Faure-Fremiet, Leon, Mayer and 

 Plantefol, 1929 and 1929a; Galadziev and Malm, 1929; 

 Nikitinsky and Mudrezowa-Wyss, 1930; Lwoff, 1932; 

 Gersch, 1937 ; Kitching, 1939, 1939a, 1939b). 



The experimental evidence accumulated by these in- 

 vestigators is unfortunately somewhat contradictory. 

 Gersch (1937) found that anaerobic conditions could be 

 tolerated for only a few seconds, an observation which 

 led him to a sharp and, it would seem, somewhat unjusti- 

 fied criticism of the work of his predecessors. A conclu- 

 sion at the other extreme was reached by Piitter (1905), 

 Nikitinsky and Mudrezowa-Wyss (1930) and Lindeman 

 (1942). Putter kept Paramaecium up to 10 days and 



