312 ARCH E. COLE 



and would soon be taken up by decaying material and organ- 

 isms, so would not remain long as such, consequently any animal 

 utilizing the oxygen would have to be in close relationship with 

 the plant remains. The burrows of chironomid larvae are 

 regularly found to be made up of a considerable amount of bits 

 of plant tissue, along with mud, and the whole cemented together 

 by a secretion from the spinning glands. The larvae are there- 

 fore in a position to utilize any oxygen which might be produced. 



DISCUSSION OF THE METABOLISM OF OTHER ANIMALS LIVING IN 



OXYGEN-FREE ENVIRONMENTS IN LAKE MENDOTA IN 



VIEW OF THE THEORIES SUGGESTED 



This hypothesis is feasible as an explanation for the oxygen 

 supply of all animals living in the stagnated region. It is 

 applicable to the clam and the annelid worm whose enzyme 

 content excludes the possibility of the production of oxygen by 

 enzymatic action within their own bodies. 



Pisidium idahoense Roper, the small clam which is regularly 

 found in the oxygen-free water in Lake Mendota, does not have 

 red blood. Neither does it contain an enzyme which is capable 

 of oxidizing guaiacum without the addition of a peroxide. How- 

 ever, it contains a peroxidase-like enzyme which is not killed by 

 boiling and which can split off atomic oxygen from a peroxide. 

 The clam is inactive during the period of stagnation. Specimens 

 kept alive in the laboratory for a period of over ninety daj^s in 

 bottles filled with a little bottom mud and oxygen-free water did 

 not change their position during that time nor were they ever 

 observed to have their valves open. Obviously, their inactivity, 

 together with the low temperature, reduces their need of oxygen 

 to the minunum. Living as they do in the mud, surrounded by 

 the remains of plants, they would be able to utilize any small 

 amounts of oxygen which might be given off by the plants, 

 which would be sufficient to keep up the low rate of oxidation 

 within their bodies. 



Experiments similar to those made with the chironomid larvae 

 were also conducted which showed that Limnodrilus sp. (?) 



