46 SURVEY OF INVERT EUR. ATHS 



Colpidium up to 16 days under anaerobic conditions. 

 Lindeman found that Frontonia and Colcps could toler- 

 ate an anaerobic medium for 30 days at 10° C. Accord- 

 ing to most other authors the survival periods range from 

 several hours to several days. 



It is quite certain that many of the variations observed 

 are correlated with the conditions under which the ex- 

 periments were conducted, but it is difficult to explain all 

 differences in a satisfactory manner. It seems doubtful 

 whether, in all cases, the oxygen was excluded sufficiently, 

 in particular in Putter's (1905) and Nikitinsky and 

 Mudrezowa-Wyss' (1930) experiments. Lindeman 's 

 (1942) procedure appears more satisfactory. As to the 

 reasons for Gersch's failure to keep his animals for any 

 length of time in the absence of free oxygen, they remain 

 obscure. 



Faure-Fremiet, Leon, Mayer and Plantefol (1929) and 

 Lindeman (1942) point out that Paramaecium and other 

 ciliates survive anaerobic conditions at to 5°C better 

 than at higher temperatures — obviously on account of 

 the lowered metabolic rate. Piitter (1905) and Barbarine 

 (1938) found that nutritional conditions are very impor- 

 tant, starving animals dying much more rapidly than 

 well-fed ones. This, too, is not surprising since during 

 anaerobiosis larger amounts of reserve substances have 

 to be mobilized than in the presence of oxygen, in order 

 to furnish sufficient energy through fermentations. 



Piitter (1905) observed also that Paramaecia sus- 

 pended in a large amount of fluid survive anaerobic con- 

 ditions better than if they are confined in a small amount 

 of medium, an observation suggesting that toxic products 

 may accumulate in the medium. It would be worthwhile 

 to repeat these experiments with bacteriologically sterile 

 cultures of ciliates in order to decide whether such toxic 

 products result from the anaerobic processes of the in- 

 fusoria themselves or whether they must be attributed 

 to contaminants of bacterial origin. This question is 



