206 ANAEROJiJC Mi'JTAIiOL/SM 



seem to be a mixture of lower and liigiier members of the 

 fatty acid series. 



Harnisch (1939) identified as end products of the an- 

 aerobic carbohydrate metabolism of the larvae of Chiro- 

 nomus thummi butyric and caproic acid. The formation 

 of these acids was more rapid in experiments lasting 8 

 to 10 hours than in those lasting from 23 to 24 hours. 

 There was no such difference in the rate of glycogen 

 degradation which was rather more rapid during the 

 later stages of the experiments, and then ''fat" {i.e., es- 

 sentially higher fatty acids) accumulated in the body of 

 the animals. Harnisch assumes that during this fat 

 formation some oxygen is liberated in an espe3ially active 

 form which would then serve to eliminate a part of the 

 lower fatty acids by oxidation. An alternate assump- 

 tion is that during longer periods of auaerobiosis the low- 

 er fatty acids are transformed into higher acids. Such 

 a process would be advantageous to the animals, since 

 "fat" is definitely less toxic than large amounts of lower 

 fatty acids. 



C. Mixed fermentations. Mixed fermentations, in 

 which lactic acid, pyruvic acid, lower or higher fatty 

 acids, dibasic acids or alcohol, appear amongst the end 

 products in various combinations or proportions, occur 

 in protozoa, worms, possibly coelenterates, and in ar- 

 thropods. We shall now review briefly the evidence 

 available for each of these groups. 



Protozoa. Among protozoa the best-known fer- 

 mentations of this type 03cur in trypanosomes, termite 

 flagellates and T etrahymena. 



Two species of trypanosomes, Trypanosoma equiper- 

 dum and Trypanosoma leivisi, were studied by Reiner and 

 Smythe (1934), Reiner, Smythe and Pedlow (1936) and 

 Searle and Reiner (1940, 1941). These investigators 

 showed that anaerobically kept Trypanosoma equipcrdum 

 transform one molecule of sue'ar into one molecule of 



