148 TRANSITION TO ANAEROBIOSIS 



high tensions. This case is not, however, unequivocal, 

 because the metabolism of this worm is characterized 

 by the persistence of anaerobic processes even in sur- 

 roundings very rich in oxygen as will be seen in more 

 detail later on. It is highly desirable that more investi- 

 gations of the nature of the end products of respiration 

 at reduced oxygen tensions be undertaken, 



B. Increase in the rate of carbohydrate consumption. 

 Again very little work has been done along this line. Von 

 Brand (1927) investigated the rates of glycogen con- 

 sumption of the polychaetes Spirographis spallanzanii 

 and Halla parthenopeia in well-aerated water and during 

 asphyxiation (which in these forms takes place while 

 there is still some oxygen left in the water). Glycogen 

 disappeared at a rate of 0.15 and 0.86 g, per 100 g. Spiro- 

 graphis in 24 hours under these two sets of conditions 

 resjDectively ; the corresponding figures for Halla were 

 0.13 and 0.71 g. It was moreover observed that 0.25 g. 

 polysaccharide was consumed daily by the latter worm 

 when kept in an aquarium which was insufficiently aer- 

 ated but in which the oxygen consumption remained 

 higher than in the asphyxiation experiments. There is 

 hardly any doubt, therefore, that these polychaetes are 

 capable of undergoing a partial transition to anaerobic 

 metabolism and of maintaining it for a limited time. 



Dausend (1931) also observed that the rate of glyco- 

 gen consumption increases in Tuhifex if the oxygen ten- 

 sion of the medium is lowered (Fig. 4). 



C. Increase in the respiratory quotient. A significant 

 increase in the respiratory quotient has been observed 

 in many cases when invertebrates were transferred to sur- 

 roundings deficient in oxygen (Table 20). The figures ob- 

 tained with marine organisms by earlier investigators, 

 like Vernon (1895), are not too reliable, owing to the 

 difficulty of determining precisely small quantities of 

 carbon dioxide in sea water bv the methods then avail- 



