422 Birge—Vertical Distribution of Pelagic Crustacea. 
to me by Messrs. Harder and Olson, and have been re-worked 
by myself and put into final shape for publication. Each gentle¬ 
man reported upon the species investigated by himself. A large 
amount of detailed work was done, especially by Mr. Olson, 
which does not appear in the following paper. No attempt has 
been made to offer the results of each set of observations. The 
value of statistical work of this kind lies rather in the average 
results obtained than in the record of each single observation. 
It is believed that the use to which this paper may be put does 
not warrant the printing of the very numerous detailed com¬ 
putations. They are, however, preserved, and can be referred 
To by any person who is interested in the subject. 
The original purpose of the investigation was to determine 
.the supposed diurnal migrations of the Crustacea, but since the 
results in this direction have been entirely negative, the out¬ 
come of the work has been to give us a definite idea of the ver¬ 
tical distribution of the Crustacea in the lake during the month 
of July. This may be called their summer position, for it 
should be expressly noted that this position is not a constant 
one during the different seasons of the year. The conditions of 
July apparently obtain through August and the greater part of 
September, but later in the year a totally different and more 
uniform scheme of distribution is developed. The conditions of 
the later spring and of June are not yet known.—E. A. B. 
LAKE MENDOTA. 
Lake Mendota, in which these observations were made, lies 
immediately to the north of the grounds of the University of 
Wisconsin, which extend for a mile along its southern shore. 
The greatest length of the lake is about 6 miles from east to 
west, and its greatest breadth is something under 4 miles. It 
is partially divided into two basins by points on the east and 
west shores, which leave between them a space of about two 
miles. The smaller or southern basin is about 3 miles in 
length. With the exception of these projections the lake is 
•quite regular iu form, being without islands and having only 
broad bays with wide mouths. The conditions of life, therefore, 
rare substantially uniform throughout the lake. 
