154 TRANSITION TO ANAER0BI08I8 



1938 and 1940; Johnson, 1942), Tubifex (J)ausond, 1931; 

 Kiiiger and Becker, 1940), Nereis (Jiirgens, 1935), Plan- 

 orhis (Leitcli, 1916; Probst, 1933) and Chironomus larvae 

 (Leiteh, 1916 ; Harnisch, 1936 ; Ewer, 1942). In several in- 

 stances results indicative of anaerobic metabolism were 

 recorded, in particular in the case of the earthworm where 

 the respiratory quotient of carbon-monoxide poisoned ani- 

 mals rose, at an oxygen tension equal to that of air, from 

 0.88 to 1.04 and at a tension of 5 per cent oxygen from 

 0.99 to 1.24 (Kriiger, 1940). 



Fewer experiments have been carried out with poisons 

 that interfere directly with the oxidation mechanisms. 

 Buchanan (1926) found that, during recovery from the 

 influence of a dilute cyanide solution, planarians consume 

 oxygen at a higher rate than usual for several hours. 

 There was, however, no clear correlation between the 

 amount of excess oxygen consumed and the length of ex- 

 posure to the poison. Buchanan therefore doubts that 

 the excess oxygen consumption is due to an accumula- 

 tion of non-oxidized substances, but he did not consider 

 the possibility that such substances may have been ex- 

 creted, at least in part (compare the above mentioned 

 experiments of Lund, 1921). Harnisch (1937b), on the 

 contrary, stated that Tubifex repays almost fully the 

 oxygen debt incurred during a period of exposure to di- 

 lute potassium cyanide. 



Fink (1926) observed that the respiratory quotient of 

 insects which had been fed arsenicals showed, in general, 

 a significant increase. However, since it remained al- 

 ways below unity, the experiments are not quite conclu- 

 sive in regard to the question under consideration. 



The case of the mite Tyroglyphus farinae, investigated 

 by Hughes (1943), is very definite. Its respiratory quo- 

 tient rose under the influence of cyanide from 0.94 to 1.32. 



B. Salinity of the medium. Kreps (1929) found that 

 the oxygen consumption of Balanus crenatus decreases 



