44 SURVEY OF INVERTEBRATES 



In buffer solutions of pH 7.3 the animals can be kept 

 alive in shallow dishes. Specht (1935) even found that 

 they disintegrate in environments completely devoid of 

 oxygen. He is of the opinion that they survive at low 

 oxygen tensions, because their normal rate of oxygen 

 consumption is low. 



C. Resistance in experimentally induced anaerobic con- 

 ditions. Many data are available on the survival of pro- 

 tozoa under experimental anaerobic conditions. They have 

 been collected in Table 9. In the following paragraphs 

 observations concerning the reactions to lack of oxygen 

 of normally aerobic protozoa will be discussed separately 

 for flagellates, rhizopods, ciliates and the cysts of these 

 organisms. 



(a) Flagellates. Little is known about flagel- 

 lates in this connection. Alexander (1931) found that 

 Euglena gracilis became motionless within 24 hours if 

 kept anaerobically in the dark. To experiment in dark- 

 ness is of course necessary with forms capable of pro- 

 ducing oxygen by photosynthesis. Von Dach (1940), on 

 the other hand, succeeded in culturing a colorless eugle- 

 noid. Astasia Mehsii, under nearly anaerobic conditions. 

 The organisms grew well, although more slowly than in 

 control cultures. A correct evaluation of these experi- 

 ments is impossible, since the data at hand do not allow 

 one to decide whether the absence of oxygen was com- 

 plete enough throughout the course of the experiments to 

 inhibit aerobic metabolism. At low temperatures va- 

 rious flagellates seem to survive quite well under anaer- 

 obic conditions (Lindeman, 1942). 



(b) Rhizopods. Rhizopods have been used more 

 extensively than flagellates for studies on anaerobiosis. 

 Ishikawa (1912), Pantin (1930, 1930a), Hulpieu (1930) 

 and Ki telling (1939, 1939b) have experimented with va- 

 rious species of amoebae. Regardless of whether the 

 large Amoeba proteus or small amoebae of the Umax 

 type were used, the amoeboid movements continued un- 



