SURVEY OF INVERTEBRATES 81 



paper (von Brand, 1938) and the account of this problem 

 as presented here is patterned along the lines developed 

 in his earlier work. Several large parasites {Ascaris, 

 Parascaris, Moniesia, Fasciola) are quite resistant in 

 experimentally induced anaerobic conditions, as was ex- 

 plained in a preceding section. Their oxygen consump- 

 tion is strictly dependent on the tension (Harnisch, 

 1933a, 1937a; Kriiger, 1936) and since the tension in the 

 intestinal lumen is low, the oxygen consumption must fall 

 far short of the maximum that they are capable of con- 

 suming at high tensions. Furthermore, even in pres- 

 ence of an abundant supply of oxygen, a large part of the 

 metabolism is anaerobic {cf. Alt and Tischer, 1931; von 

 Brand, 1934a). The conclusion thus seems inescapable 

 that when the worms are in their normal habitat anaero- 

 bic respiration markedly predominates. One is there- 

 fore justified in considering these animals as predomi- 

 nantly anaerobic. 



There are some clear indications, however, that, at 

 least in Ascaris, even the small amount of oxygen pres- 

 ent in the intestine may take part in metabolism. The 

 asearids have some haemoglobin (Flury, 1912; Kriiger, 

 1936), w^hich will assist them in gathering oxygen at low^ 

 tensions. Another imjDortant observation is that made 

 by Slater (1925) according to which death was more rapid 

 in electrically stimulated specimens under anaerobic than 

 under aerobic conditions. Finally, von Brand (1937) 

 demonstrated that Ascaris is able to resynthesize some 

 glycogen in a jDcriod of aerobic metabolism following one 

 of anaerobic metabolism. The occurrence of such a clearly 

 aerobic process could hardly be understood unless it ex- 

 isted also in nature.. 



Other helminths are probably capable of leading a 

 more aerobic life in the intestine. They may either get 

 significant amounts of oxygen from the blood which they 

 withdraw from the host, as happens in the case of hook- 



