314 ARCH E. COLE 



SUMMARY AND CONCLUSIONS 



The results of the work thus far accomplished may be summar- 

 ized as follows: 



1. During certain periods of the year the water in the deeper 

 parts of Lake Mendota contains no dissolved oxygen which can 

 be detected. Nevertheless, several animals are able to lead a 

 more or less active life in it and liberate energy for the mainte- 

 nance of their normal physiological processes. 



2. Theories as to the sources of their energy have been advan- 

 ced. That the animals are facultative anaerobes, dependent upon 

 oxygen from some source for the liberation of the potential energy 

 stored up within their bodies, is highly improbable. It is 

 thought that an incomplete breakdown of compounds, anoxybiosis, 

 would not suffice to be an explanation of the source of the energy 

 exhibited by many of the active animals. 



3. As to the supply of the oxj^gen necessary to liberate energy, 

 three theories have been set forth : 



a. That oxygen is stored by the haemoglobin in times of 

 oxygen plenty and then gradually used up in times of oxygen 

 want, has been suggested. Not all the animals, in fact only a 

 few, living in the stagnated region have haemoglobin; and even 

 if they did, Leitch ('16) has demonstrated that the amount of 

 oxygen which the haemoglobin is chemically able to fix and hold 

 is negligible when compared with the amount necessary to- 

 liberate the energy expended during the total time when the 

 dissolved oxygen is lacking in the surrounding water. 



h. That the supply of oxygen is dependent upon the presence 

 of an enzyme, complex which is capable of building up a peroxide 

 and then splitting off oxygen from it, is a possibility for some 

 of the organisms at least. However, with the data at hand, this 

 does not seem probable, inasmuch as the production of atomic 

 oxygen could not be demonstrated when the conditions of the 

 the experiments excluded the presence of molecular oxygen. 

 Although further work may show that such a process furnishes 

 an oxygen supply for certain animals, the theory makes no 

 provision for other animals which live in the same environment 



