32 THE LIFE OF DEVTT.S LAKE 



Dr. Heath in ms. notes thus summarizes the results of his work 

 on Devils Lake : 



"The waters of the Lake seem to carry no dissolved hydrog:en 

 sulphide except in a few places where contaminated by sewage. The 

 mud on the bottom and the water in immediate contact with it 

 carry the gas in small amounts." 



Comparatively little is known regarding the relation between 

 dissolved nitrogen and aquatic life. It probably is always present 

 in water, forming a large percentage of the dissolved gas. Judging 

 by its inert character, it seems improbable that it plays any import- 

 ant part in the life of aquatic animals, although there is some 

 evidence to show that in excess it may be injurious to fishes (Marsh 

 and Gorham, 1905). It may possibly be an important part of the 

 food of aquatic plants, though this is not definitely known. 



But two tests have been made for nitrogen in Devils Lake, both 

 in the summer of 1914. Two 1200 cc samples gave by the boiling 

 method 84.9% and 89.8% respectively of nitrogen in the dissolved 

 gases, the remainder being oxygen. In these two tests no methane, 

 carbon monoxide or free hydrogen were detected. These are the 

 only tests which have been made for these gases. 



BIOLOaY 



The biological investigation of any area comprises an enumer- 

 ation of its inhabitants, and a determination of their distribution 

 and abundance in time and space, in reference to their physical 

 environment and their reactions upon one another. Without the 

 cooperation of many specialists the first phase of the problem is 

 impossible, while the second phase is of course dependent on the 

 first. Due acknowledgment of the aid received in the prosecution of 

 this work has already been made and need not be repeated here. 

 The list of species is admittedly incomplete since some of the iden- 

 tifications have not been finished, and part of the work was pre- 

 liminary in character. This is notably true of the nematodes, 

 insects, and bacteria. 



In spite of these deficiencies, however, it has not seemed advis- 

 able to delay publication further, since to obtain complete lists of 

 species would probably require several years delay, and by that 

 time the fauna and flora of the lake would probably differ markedly 

 from their composition when the work Avas begun. In fact at the 

 present time distinct changes have taken place, and in the case of 

 some parts of the lake (East and Mission Lakes) the present fauna 

 and flora have little resemblance to those of a few years previous. 

 Furthermore, the data at present available are sufficient to give a 

 fairly adetiuate idea of the life of the lake and its responses to its 

 changing environment. 



