SURVEY OF INVERTEBRATES 115 



whether these findings might not somehow tie up with 

 earlier observations of Cole (1921) who had found in 

 the body of Chironomiis tcntaus an enzymatic complex 

 capable of building up peroxide from which, under cer- 

 tain conditions, oxygen was split off. 



Ssinitza (1936) observed another difference between 

 the chironomid larvae which contain haemoglobin and 

 those which do not. While the oxidation-reduction po- 

 tential was about the same in the two groups if the ani- 

 mals were kept in oxygenated surroundings, it was con- 

 siderably lowered in the haemoglobin-containing species, 

 and was maintained at about its original level in the spe- 

 cies without that pigment, when the animals were kept 

 in oxygen-free water. The implications, however, of this 

 difference do not seem to the present writer to be suffi- 

 ciently clear to allow speculations on ecological problems. 

 The case of the Chaohorus larvae has been much less 

 analyzed than that of the chironomids. It is well known 

 that these larvae are recovered quite often from the oxy- 

 gen-free deep zones of eutrophic lakes (Appendix, Table 

 3) and Lindeman's (1942) experiments have demon- 

 strated that they possess an extremely well-developed to- 

 lerance for experimentally induced anaerobic conditions 

 ( Table 14) . There is some doubt as to the extent to which 

 they will actually stay confined in nature to the truly 

 anaerobic layers. They possess a well-developed hydro- 

 static apparatus which enables them to rise to the surface. 

 According to Juday (1921)— compare also Eggleton, 

 1932 — Chaohorus puuctipennis stays in the deep zone 

 only during the day, during the night it rises to the 

 surface strata. Obviously, it can frequently get oxygen 

 there ; but in the winter this mechanism is of no avail if 

 the oxygen disappears from the whole water column 

 under the ice. The anaerobic metabolism of these ani- 

 mals has unfortunately never been investigated ; it would 

 provide interesting problems. 



