OXYGEN SUPPLY OF CERTAIN ANIMALS 313 



although it possesses red blood, apparently does not contain an 

 enzyme complex capable of exidizing guaiacmn without the 

 addition of a peroxide. This annelid has an iron-containing 

 enzyme-like substance which is not killed by boiling and which 

 can split atomic oxygen from a peroxide. It lives in tubes 

 constructed of the mud and small bits of plants. In the labora- 

 tory it is also found among the tubes of chironomid larvae. 

 Its association with plant remains would enable it to obtaian 

 from them any oxygen which might be liberated. 



The larvae of Sialis infumata Newman, the black-winged orl 

 fly, which are only occasionally found in the stagnated region 

 in Lake Mendota, are very active. They are more or less 

 predacious, crawling in and over the mud and preying upon 

 such smaller organisms as they can find. They are also reported 

 to eat mud containing organic material. Sialis larvae have no 

 haemoglobin in their blood, and their tissues contain very little 

 of the enzyme-like substance which requires a peroxide for the 

 oxidation of guaiacum. This is quite different from the case of 

 the chironomid larvae. However, the inner surface of the 

 chitin of the Sialis larvae contains a thermolabile enzyme complex 

 which will of itself, without the addition of a peroxide, oxidize 

 guaiacum, but not so strongly as that in the chironomid larvae. 



This second case of the presence of an enzyme complex which 

 is capable of yielding an oxidizing substance — probably atomic 

 oxygen — is additional evidence for the theory that at least a 

 part of the oxygen supply of the more active animals living in 

 water in which no dissolved oxygen can be demonstrated may 

 come from a splitting off of oxygen from a previously built-up 

 peroxide, the whole being due to enzymatic action. 



No work was done on the protozoans, the gastrotrich, or the 

 ostracod, which are also normally found living in the stagnated 

 region of Lake Mendota. 



