PLACE OF ANAEROB. IN METABOLISM 259 



oxidations in aerobic conditions (so-called "aer- 

 obic fermentations"). 



(a) E u r y a n o X y b i o t i c a e r o - f e r ni e n- 

 t e r s : animals with a well-developed anaero- 

 bic metabolism, allowing them to survive for 

 a long time under anaerobic conditions. Ex- 

 ample : many parasitic worms. 



( b) S t e n a n o X y b i o t i c a e r o - f e r m e n- 

 t e r s : animals in which the anaerobic me- 

 tabolism is not well enough developed to allow 

 long survival under anaerobic conditions. Ex- 

 ample : trypanosomes. 



(2) Holo-oxidizers: animals in which the metabo- 

 lism in the presence of air consists exclusively 

 or predominantly of complete oxidations. 



(a) Euryanoxybiotic holo-oxi- 

 dizers : animals with well-developed an- 

 aerobic functions under anaerobic conditions. 

 Example: some parasitic worms (TricJiindla 

 larvae), probably Owcnia. 



(b) S t e n a n o X y b i o t i c holo-oxi- 

 dizers : animals with a poorly developed 

 anaerobic metabolism, not sufficient to allow 

 survival for long periods under severe lack of 

 oxygen. Example : many insects, cephalo- 

 pods. 



The group A in this classification calls for some fur- 

 ther discussion. While the obligatory anaerobic inver- 

 tebrates are injured rapidly by oxygen at a tension of 

 about one atmosphere and probably at somewhat lower 

 tensions (Wetzel, 1928; Liebmann, 1936; Lackey, 1932; 

 Trager, 1934; Westphal, 1934; Hungate, 1939, 1941, 1942; 

 Hastings, 1944), it has never been ascertained whether 

 extremely low tensions are also toxic. Indeed, the fact 

 that termite flagellates can be cultured successfully in 



