of the organisms inhabiting the lake, together with physical and 

 chemical studies of its water, have been made at freqvient intervals 

 from 1911 to 1914 with the exception of certain periods in 1912 and 

 1913, during which time the absence of the writer interfered with 

 the conduct of the work, and during the winter when few collections 

 were made. A few collections were made in 1909 and 1910, but 

 these were preliminary to the main series. An additional series was 

 also made between December, 1922, and July, 1923. The collections 

 and determinations, aside from the purely preliminary work, have 

 thus covered a period of twelve years (1911-1923). 



The major part of the work has been devoted to a study of the 

 plancton of the lake in its ecological relations, this forming the most 

 important part of the life of the lake. Several general chemical anal- 

 yses (both organic and inorganic) have been made during the study, 

 and analyses of certain constituents, especially the ammonias, nitrates, 

 nitrites, carbon dioxide and oxygen, have been made during part 

 of the time at much more frequent intervals. This will be explained 

 in detail in the proper place. In connection with the collections and 

 analyses temperature records have been kept, and a study of the 

 distribution of light at various depths has been made. The data of 

 the U. S. Weather Bureau Station in the city of Devils Lake, eight 

 km. distant, have been drawn upon extensively, and these have been 

 amplified to a certain extent b}^ our own more or less fragmentary 

 records of air temperatures and precipitation taken at the station. 



There are several reports on various phases of the biology of 

 the Devils Lake region beginning with that of Pope (1908), but 

 nothing as yet of a comprehensive nature. There are brief notes 

 on the physiography of the region in Upham (1896) and Willard 

 (1921), while Simpson (1912) gives a thorough treatment of this 

 subject. 



