SURVEY OF INVERTEBRATES 105 



and that the radium emanation present in the thermal 

 water is only partially responsible for this effect. 



Levin (1933) found that the asphyxiation of C rang on 

 vulgaris is retarded if certain vital dyes are added to 

 the sea water {e.g., neutral red, 1: 50,000; Bismarck 

 brown, 1: 100,000; or methylene blue, 1: 50,000). In a 

 second paper (1933a) he reported that the survival period 

 of this shrimp in oxygen-poor water was shorter if small 

 amounts of arsenious acid plus neutral red were added 

 than if the water contained either of these substances 

 alone. Under conditions of good oxygenation, on the 

 other hand, an opposite effect was observed, the sur- 

 vival being better when both substances were present to- 

 gether. 



2. AQUATIC INSECTS 



I. LAKVAE 



Larvae of insects leading an aquatic life are found in 

 several habitats which are poor in oxygen or without oxy- 

 gen. Lauterborn (1916) reports the larvae of Eristalis 

 tenax in sapropelic ponds. One may doubt, however, 

 whether this actually implies an anaerobic life. It seems 

 quite possible that these larvae regularly get oxygen from 

 the surface by means of their long prehensile tail which 

 represents a respiratory syphon. 



As to Donacia larvae, they occasionally get only small 

 amounts of oxygen from their surroundings. Their nor- 

 mal oxygen supply is derived from the airspaces of sub- 

 merged aquatic plants (Boeving, 1910; Deibel, 1911). The 

 oxygen concentration in this air can at times be very 

 low as has been pointed out previously. But recent ex- 

 periments (Hoffman, 1940) have demonstrated that these 

 larvae are also capable of utilizing directly the oxygen 

 dissolved in the water. Nevertheless, most investigators 

 agree (see Table 14) that the Donacia larvae are very 

 resistant in experimentally induced anoxic conditions. 

 The seemingly contradictory observation of Nikitinsky 



