SURVEY OF INVERTEBRATES 121 



used at an early date (Lyonet, 1762; Treviranus, 1814; 

 Straus-Durkheim, 1818) has been followed until recently 

 (Plateau, 1872; Devaux 1891; Gauckler, 1897; Fielde, 

 1904, 1904a; Bruneteau, 1931). The figures found in 

 such experiments are open to serious objections. In 

 many cases no attention was paid to the question whether 

 or not the animals were thoroughly wetted when im- 

 mersed, i.e., whether they were not surrounded by a sheet 

 of air that would set up a mechanism similar to that out- 

 lined above for aquatic insects. 



Furthermore, the metabolism could still have been 

 aerobic in part, even if the animals had no air bubbles 

 close to their body. Fraenkel and Herford (1938) show- 

 ed that at least some insect larvae, amongst them the 

 rather heavily chitinized Tenebrio larva, have a quite 

 marked cutaneous respiration when immersed in water, 

 a respiration which amounted, in the latter case, to about 

 20 per cent of the normal. It is likely that the extent of 

 the anaerobiosis induced by immersion in oxygen-con- 

 taining water will vary greatly with the species employ- 

 ed. Bodine (1928) states that he observed, with grass- 

 hoppers, the same survival irrespective of whether he im- 

 mersed them in water or whether he established strictly 

 anaerobic conditions by employing atmospheres of hydro- 

 gen, carbon dioxide or nitrogen. 



Some other investigators immersed insects into water 

 from which oxygen had been partly removed by boiling 

 (Nigmann, 1908; Deibel, 1911). That, of course, re- 

 duced the possible cutaneous respiration almost to the 

 vanishing point. Nonetheless, one can still object that 

 the results obtained in that manner, as in all immersion 

 procedures, are complicated by secondary elfects which 

 the water itself may have on the animals. 



A last group of investigators either introduced the 

 organisms into an atmosphere of inert gases, a pro- 

 cedure much less open to objection (Hausmann, 1803; 



