56 SURVEY OF INVERTEBRATES 



ganism may require more oxygen than other intestinal 

 protozoa. 



A different situation seems to prevail in the rumen 

 ciliates, organisms which are very sensitive to oxygen 

 (Westphal, 1934; Hungate, 1941 and 1942) and appear 

 to be truly anaerobic. This is remarkable since large 

 amounts of oxygen will doubtless reach the stomach of 

 ruminants from time to time, although this oxygen dis- 

 appears rapidly, due to the pronounced bacterial activity 

 in the rumen. The above-outlined possibility of locally 

 prevailing anaerobic conditions in the microatmosphere 

 may allow these parasites to survive until the excess oxy- 

 gen has disappeared from the macroatmosphere. 



When certain protozoa, like Balantidium coli or Enda- 

 moeha histolytica migrate from the intestinal lumen into 

 the tissues, the whole situation changes. It is probable 

 that, in their new habitat, they have regular access to 

 the same amounts of oxygen as the surrounding cells of 

 the host. Whether this oxygen is sufficient to cover their 

 maximum consumption is another question, the answer 

 to which will require more knowledge concerning the 

 oxygen relationships of these organisms. 



2. PROTOZOA OF THE ALIMENTARY TRACT OF INVERTEBRATES 



The only protozoa inhabiting the alimentary tract of 

 invertebrates for which a pronounced ability to live an- 

 aerobically has so far been demonstrated are the flagel- 

 lates occurring in the intestine of the termites. They 

 are, in vitro, rapidly injured and killed by oxygen (Tra- 

 ger, 1934; Hungate, 1939) and the same holds true in 

 nature, as Cleveland's (1925) well-known defaunation 

 method by oxygenation indicates. Trager (1934) further- 

 more showed that the following termite flagellates can 

 be cultured for various lengths of time if the culture me- 

 dium is overlaid with a vaseline seal, i.e., if the oxygen 

 supply is reduced: Trichomonas sp., Trichomonas term- 

 opsidis, Tricercomitus termopsidis and Trichonympha 



