102 PROTOZOOLOGY 



to live in water containing no free oxygen. For example, Noland 

 (1927) observed Metopus es in a pool, 6 feet in diameter and 18 inches 

 deep, filled with dead leaves which gave a strong odor of hj^drogen 

 sulphide. The water in it showed pH 7.2 at 14°C., and contained no 

 dissolved oxygen, 14.9 c.c. per liter of free carbon dioxide, and 78.7 

 c.c. per liter of fixed carbon dioxide. The parasitic Protozoa of 

 metazoan digestive systems live also in a medium containing no 

 molecular oxygen. All these forms appear to possess capacity of 

 splitting complex oxygen-bearing substances present in the body to 

 produce necessary oxygen. 



Several investigators studied the influence of abundance or lack 

 of oxygen upon different Protozoa. For example, Putter demon- 

 strated that several ciliates reacted differently when subjected to 

 anaerobic condition, some perishing rapidly, others living for a con- 

 siderable length of time. Death is said by Lohner to be brought 

 about by a volume-increase due to accumulation of the waste prod- 

 ucts. When first starved for a few days and then placed in anaerobic 

 environment, Paramecium and Colpidium died much more rapidly 

 than unstarved individuals. Putter, therefore, supposed that the dif- 

 ference in longevity of aerobic Protozoa in anaerobic conditions was 

 correlated with that of the amount of reserve food material such as 

 protein, glycogen and paraglj^cogen present in the body. Putter fur- 

 ther noticed that Paramecium is less affected by anaerobic condition 

 than Spirostomum in a small amount of water, and maintained that 

 the smaller the size of body and the more elaborate the contractile 

 vacuole system, the organisms suffer the less the lack of oxygen in 

 the water, since the removal of catabolic products depends upon these 

 factors. 



The variety of habitats and results of artificial cultivations of 

 various Protozoa indicate clearly that the oxygen requirements vary 

 a great deal among different forms. Attempts were made in recent 

 years to determine the oxygen requirement of Protozoa. The results 

 of the observations are not always convincing. The oxygen consump- 

 tion of Paramecium is said, according to Lund (1918) and Amberson 

 (1928), to be fairly constant over a wide range of oxygen concentra- 

 tion. Specht (1934) found the measurements of the oxygen con- 

 sumption and carbon dioxide production in Spirostomum ambiguum 

 vary because of the presence of a base produced by the organism. 

 Soule (1925) observed in the cultural tubes of Trypanosoma lewisi 

 and Leishmania tropica, the oxygen contained in about 100 c.c. of 

 air of the test tube is used up in about 12 and 6 days respectively. 

 A single Paramecium caudatum is said to consume in one hour at 



