RECOVERY FROM A^AEROBIO^J^ 251 



hour period of deprivation of oxygen, leeches [Hirudo 

 mecUcinalis) excrete a much larger quantity of nitrogen- 

 ous substances than if they are exposed to the anaerobic 

 conditions alone. This increase was observed in all de- 

 termined fractions (total non-protein nitrogen, ammonia, 

 amino-acids and creatinine). An increase in post-anaero- 

 bic ammonia excretion was also described by Harnisch 

 (1943) for the larva of Chironomus batliophilus. In neith- 

 er of these cases, however, is it clear whether the in- 

 creased elimination was simply due to an impaired excre- 

 tion during the anoxic period or to true recovery processes, 

 i.e., it is not yet definitely known whether these various 

 substances themselves or their partially decomposed pre- 

 cursors had accumulated in the bodv. 



