64 THE LIFE OF DEVILS LAKE 



curs occasionally iu the East Lake collections, but the records are 

 very few. M. elegans has been found in Mission Lake only. 



Tetrapedia gothica. "Sparingly found in two collections, one 

 from towings, the other associated with Cladophora near the shore 

 in front of the laboratory. This, so far as is known, is the first 

 recorded collection of this genus in the United States, and it is like- 

 wise the first time the species has been found since its original dis- 

 covery by Reinsch in Germany." 



Tetrapedia sp. has been found in Spring Lake. 



Arthrospira jenneri. occurs occasionally in Main, East and Mis- 

 sion Lakes. 



Oscillatoria. This genus is represented by ten species, one of 

 them indeterminate. Of these amphibia is 'the most abundant and 

 widely distributed." Specimens of Oscillatoria occur occasionally 

 in the plancton collections, but not often enough to warrant any 

 counclusious relative to its seasonal distribution. Beside amphibia 

 the following species occur, hrevis, chalyhea, chlorina, geminata, 

 janthiphora, Umosa, suhtilissima, tenuis and sp-, "a small form 

 . . . resembling in a general way the descriptions of O. sub- 

 tilissima. ' ' 



Plectonema tenue. "Numerous filaments of this species were 

 obtained from surface tow in one of the smaller bays of the lake. 

 While it is probable that the material had become detached from 

 stones, a search along the shore in shallow water failed to reveal 

 any indication of from where the specimens had come." 



Spirulina. This genus is also of sporadic occurrence in the 

 plancton samples, and hence is not represented in the charts. Of 

 the four species present, major, nordstedtii, suhtilissima and tener- 

 rima, the first is the most common. Nordstedtii and suhtilissima 

 are of interest as being the only salt water representatives of either 

 Myxophyceae or Chlorophyceae present in the lake. 



Anahasna, represented by two species, flos-aquae and spiroides. 

 occurs rarely. It is found occasionally in the plancton collections, 

 but the data do not enable me to draw any conclusions regarding its 

 seasonal distribution. 



Lyngbya conlorta was formerly one of the most characteristic 

 forms of the plancton (pi. 14). 



In 1911, 12 and 14 it was abundant from September on to the 

 season's close*, while in 1913 it showed a great decrease in Septem- 

 ber and October. In both 1912 and 13 a distinct maximum occurred 

 at the end of May and early June, while in 1914 this maximum, 

 tho present, was very small. In 1913 a very large and well marked 

 maximum occurred about the middle of August, and apparently a 

 similar maximum occurred about two weeks later in 1912. In 1914 



♦In 1914 this' \v;is on Septt-niljcr 14. 



