58 THE LIFE OF DEVILS LAKE 



species in the enumeration, and the form specified probably includes 

 several. It is designated by form simply as Micrococcus. Besides 

 these a less frequent type, Sarcina, is of common occurrence. 



The bacteriology of Devils Lake was studied during the sum- 

 mer of 1916 by Mr. (now Dr.) Fi. "W. Stevenson, a pre-medical 

 student of the University, under the direction of Dr. L. D. Bristol, 

 then director of the Public Health Laboratory of the State. The 

 methods followed by Mr. Stevenson are those recommended by the 

 American Public Health Association in their "Standard Methods of 

 Water Analysis." 



Samples for quantitative analysis were collected in the morn- 

 ing, shipped to the University in an iced container, and plated in 

 the evening of the same day. With those intended for qualitative 

 analysis only, especially with those from outlying parts of the lake 

 complex, several days elapsed in some instances between time of 

 collection and plating, and no attention was paid to keeping the 

 sample at a low temperature. In collecting samples from points 

 below the surface of the lake, the apparatus illustrated in figure 16 

 was employed. It consists of a metal frame f, weighted at the 

 bottom with a block of lead. w. The frame carries a collar c, one 

 side of which is hinged and can be swung open to admit a bottle, 

 the latter being held in place by screwing the two parts of the coi- 

 lar together at s. The stopper of the bottle is held by a screw clamp 

 k, at the base of a rod, r, which latter is attached to a cord, 1, and 

 surrounded by a spring, p. The rod, r, passes thru a collar, d, which 

 is bolted to the top of the frame by means of a nut, n. The frame 

 is suspended by two cords, m, which are attached to a small plate, 

 h, thru a collar, e, at the center of which the cord, 1, passes, and 

 which is in turn suspended by a line, t. The apparatus is lowered 

 into the water to any desired depth by the line t, when a pull on 

 the cord, 1, removes the cork and allows the bottle to fill. When 

 the latter is full, the cork is replaced by repleasing the tension on 

 the spring, p. 



The seasonal distribution of bacteria is indicated by the curves 

 for Micrococcus platted from the planeton counts (pi. 11). They 

 show, in general, an enormous development in summer, with a 

 marked decrease or total disappearance in winter. Further than 

 this, it is difficult to draw any general conclusions from the dis- 

 tribution curves, as they differ considerably in different years. 



In 1912 and 1913 definite maxima occur about June 1 with 

 indications of a mid-summer minimum and a small maximum near 

 the end of August, at least in 1913. In 1911 a minimum is indicat- 

 ed about August 15, tho the records here are too few to warrant 

 definite conclusions. In 1914 there is a June maximum without, 

 however, any sharply marked peak, and a very distinct minimum 

 al)ont Jnlv 20. ffdlnwed bv a great increase in August. The 1914 



