THE LIFE OF DEVILS LAKE 105 



is 560,000. The maximum for the lakes studied by Birge & Juday 

 was about 40,000 pr. em. for Cayuga Lake, while the others were 

 distinctly lower. 



In a recent paper by Kemmerer et al. (1923) there are data for 

 51 lakes in the northwestern United States. I have computed the 

 averages for a fe-sv of these, chosen more or less at random, but in- 

 cluding both deep and shallow lakes. The maximum number of 

 Crustacea was 212,400 for Calvert Lake, Washington, a small lake 

 about 12 m. deep. The other lakes ran very much lower than this. 

 The rotifer maximum for these lakes was 34,000 pr. cm. in Cottage 

 Lake, Washington on August 13, 1913. Here, too, it should be re- 

 membered that these averages are, in most cases, for only a single 

 series of collections. 



The data for the nannoplancton have, in most cases, been based 

 on net collections, and hence are much below their true values. 

 Birge & Juday (1923), however, give some data from centrifuged 

 collections. Neither method, however is closely comparable with the 

 Sedgwick-R after method, which stands between the other two in 

 respect to the amount of nannoplancton recorded by it. 



The average number of diatoms in Devils Lake for the years 

 1911- '14 inclusive is 50,000 pr. cm. which is higher than most of 

 the figures recorded by Kemmerer et al. (I.e.),* altho in a few 

 instances their figures are very much higher, ^t is in every 

 instance far below the figures given by Birge & Juday (1921) for 

 their centrifuged samples, and in several cases lower than their 

 results for the net plancton. 



I have attempted no comparison for the other algae for the 

 additional reason that many of my results are in "standard 

 units,"** or mm., while other authors state their results in colonies 

 or filaments. 



Devils Lake may be compared to a large pool, where, finding 

 conditions favorable to existence, and little competition, and there 

 being no flow to carry them away as they multiply, certain types 

 of life have developed extensively; while others have developed 

 slightly, or not at all, in an environment, which is unfavorable to 

 them. Rate of reproduction enters here, of course, as an important 

 factor, and the whole question is complicated and obscure. 



The study of the lake has revealed new species as follows: 

 Protozoa — Urotricha labiata, Gerda annulata, (Edmondson 1920) ; 

 Diatoms — Chaetoceros elmorei, Navicula minnewaukonensis, (Elmore 

 1921) : Rotifiers — Brachionus satanicus, B. spatiosus and B. 

 pterodiuoides, (Rousselet 1911, 12 & 13) ; while several hitherto known 



♦In Tipper Klamath Lake, Orejron, on July 20, 1913 there waa the large average 

 of more than 20.000,000 pr. cm. This is a shallow lake in most of its area, with 

 a maximum depth of about 11 tn. 



•*Seo Whipple (1914). 



