THE LIFE OF DEVILS LAKE 107 



enee of animal life. Recently, however, Juday (1908) has found 

 many species of animals living in the bottom of Lake Mendota, in- 

 cluding several Protozoa, rotifers, annelids, crustaceans, insect lar- 

 vae, a nematode, and a mollusc. Juday has shown very clearly the 

 absence of dissolved oxygen in the bottom water of Lake Mendota 

 at certain seasons, both by boiling and titration tests. 



In my own work on Devils Lake I have used exclusively th« 

 latter method, which, as already noted,* is probably not very ac 

 curate in alkaline water. The decaying character of the ooze, 

 which has a very foul odor, is strong presumptive evidence, however, 

 which, together with the titrations and the results of Juday 's work, 

 renders it practically certain that the bottom ooze of Devils Lake is 

 frequently oxygen free. 



In this ooze I have found several species of Protozoa and a 

 red Chironomus larva, while in the water immediately overlying the 

 ooze, which showed no oxygen by titration, I have found Diaptomus, 

 Moina, Cyclops and nauplii, in addition to the Protozoa. These 

 animals may, however, have been temporary invaders of this layer, 

 which is never very thick. 



As yet we have no satisfactory explanation of the way in which 

 these animals live in an oxygen-free environment, tho various ex- 

 planatory theories have been advanced, which have been discussed 

 at some length by Cole (1921). 



In any study of distribution of either animals or plants, one 

 finds some wide-spread, adaptive species, and others of restricted 

 distribution. The latter may not necessarily be non-adaptive, how- 

 ever, since the question of ease of dispersal enters into any prob- 

 lem of distribution. 



The questions of adaptability and dispersal lead up to that of the 

 source of the life of Devils Lake. While it is possible to trace with 

 a fair degree of probability the origin of land floras and faunas, 

 from the distribution of both living and extinct forms ; this is 

 much more difficult in the case of aquatic organisms, especially 

 those of the plancton ; because of their ease of dispersal and conse 

 quent wide spread distribution; their great adaptability, in many 

 cases, to widely different environments, and especially to our lack 

 of knowledge concerning the distribution of many of them. 



Thus, in at least three cases, in the present stud}'** organisms 

 have been recorded for the first time in North America, and in a 

 recent paper on the algae of several other North Dakota lakes by 

 Moore and Carter several other species are recorded as new to 

 America. 



Diaptomus sicilis has hitherto been considered as a cold water 

 species. Thus, according to Marsh in Ward & Whipple (1918) it oc- 



*See p. 30. 

 **See p. 106. 



