Marsh — Limnetic Crustacea of Green Lake. 185 



For winter work, the apparatus is hung from a tripod placed 

 over a hole in the ice. (Plate XIV.) 



The tube at the bottom of the bucket was made of a size to 

 fit in the top of an eight drachm homeopathic bottle, and in or- 

 der to preserve material, I simply washed it with strong alcohol 

 immediately from the bucket into the bottle. 



A buoy was anchored in from forty to forty-five meters of 

 water, and all collections were made from that point. In suc- 

 cessive years the buoy was located in very nearly the same 

 place, and when collections were made through the ice, it was 

 intended that they should be taken at nearly the location of 

 the buoy. 



Collections were made in all kinds of weather, but more were 

 made in comparatively pleasant weather, as naturally one would 

 prefer to visit the lake under such conditions. 



The record of observations was kept in a book arranged for 

 the purpose. A sample page of this book appears on the next 

 page. 



The temperatures were taken by a Miller-Casella deep-sea 

 maximum and minimum thermometer, which was loaned to me 

 by the United States Fish Commission for the purpose. As those 

 who have used this form of thermometer know, it is very slow 

 in its action, it being necessary to allow at least twenty min- 

 utes for each observation. This made it impossible for me to 

 get a record of temperatures at intermediate depths, although 

 such a record is very important in determining the laws gov- 

 erning the vertical distribution. 



The temperature curves of the two years, 1895 and 1896, are 

 shown in plates V and VI, with the exception that no observations 

 were made in July and August, 1895. It will be noticed that 

 the maximum range of bottom temperature observed was from 

 35 to 45 degrees, thus indicating great uniformity of conditions 

 of temperature at the bottom. 



