304 ARCH E. COLE 



for transporting oxygen would be developed in an animal which 

 would not use it all the time. Such a development is especially 

 questionable when it is considered, as will be pointed out later, 

 that the haemoglobin becomes functional only when the oxygen 

 pressure is low. 



The point made here is this; the incomplete breakdown of 

 food-stuffs in the absence of oxygen within the body of the 

 chironomid larvae offers a possible source of energy, though it is 

 not thought to be the probable one. 



2. Haemoglobin as a storehouse for oxygen 



It has been suggested by Maill and Hammond ('00) and sug- 

 gested again by Pause ('18) that the haemoglobin of the blood 

 may perhaps act as a storehouse for oxygen; that in times of 

 sufficient oxygen supply the haemoglobin stores up oxygen which 

 is then used when the supply in the surrounding medium has 

 become exhausted. 



Leitch ('16) estimated by the use of Krogh's microrespiratory 

 apparatus that, "ten chironomus larvae weighing .16 gr. used 

 .428 c. mgr. of oxygen in one minute. Chironomus has 50% 

 of blood of an oxygen capacity of 6 c.c. pc, i.e. these ten larvae 

 had .08 c.c. of blood whose total oxygen capacity was .0048 

 c.c. oxygen." This would suffice to store oxygen sufficient for 

 about twelve minutes. 



The ability of the haemoglobin of the chironomid larva to 

 store up sufficient oxygen to last throughout the stagnation 

 period is out of the question. However, the importance of 

 haemoglobin must be admitted. In invertebrates, haemoglobin 

 is found in the representatives of many species in many phyla, 

 and its presence is always connected with a poorly oxygenated 

 medium in which the various animals live. Undoubtedly, there 

 is some correlation between the two facts. Leitch showed that 

 down to an oxygen pressure of 7 mm. the chironomid larvae do 

 not use their haemoglobin at all, the needs being supplied by 

 physical solution. But below this point the haemoglobin is 

 used to chemically combine with oxygen and transport it at 

 oxygen pressures so low that the required amount is not supplied 

 by simple physical solution. 



