SURVEY OF IXTERTEBRATES 113 



Harnisch (1929) measured the oxygen consumption of 

 some cliironomids at various tensions and determined the 

 point at which the oxygen consumption begins to drop. 

 He found that the animals should be classified as fol- 

 lows, if one considers the order of decreasing oxygen ten- 

 sion that they require to maintain the normal oxidative 

 level: Prodiamesa - Microtendipes - Eutanytarsus - 

 Chironomus. Of these species only Prodiamesa is with- 

 out haemoglobin. But, as Harnisch points out, if one 

 considers the normal distribution in waters of decreasing 

 oxygen content, the order is the following: Eutanytarsus 

 - Microtendipes - Prodiamesa - Chironomus. Obviously 

 there is no connection between the ecological distribution 

 and the possibility or impossibility of maintaining a 

 maximal oxygen consumption at low tensions. 



This negative result led Harnisch (1933) to investigate 

 whether it might not be possible for various chironomids 

 to supplement the failing aerobic oxidations by anaerobic 

 processes. He measured the amount of carbon dioxide 

 produced and the amount of oxygen consumed at low 

 tensions, and since any excess of carbon dioxide over that 

 which was formed from the consumed oxygen, could not 

 have originated from aerobic oxidations, he considered 

 the ratio, excess carbon dioxide to oxygen, as a measure 

 of the extent of the anaerobic processes that substitute 

 for aerobic oxidations. The higher the quotient was, the 

 better the mechanism for anaerobic respiration was de- 

 veloped. He found the following figures : Eutanytarsus : 

 22.5, Prodiamesa : 30.8 and Chironomus : 36.1. It is evi- 

 dent that this series agrees well with the one given above 

 for the ecological oxygen demand and this agreement is 

 certainly suggestive. 



However, Harnisch in a later publication (1937) em- 

 phasized that a great many experimental errors accum- 

 ulate in these figures and render them rather unreliable. 

 He seems inclined to seek another explanation for the 

 ecological observations. Aerobic animals subjected to 



