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. 
