192 
Marsh—Limnetic Crustacea of Green Lake. 
diaptomus — continued. 
No. 
of Coll. 
Total 
No. 
Per cent 
0-5 
5-10 
10-15 
15-20 
20-25 
25-30 
30-35 
35-40 
40- 
9.96.. 
2,392 
56.52 
25.09 
10.70 
5.02 
.75 
.50 
.25 
.12 
1.05 
10.96.. 
2,354 
39.50 
33.30 
8.84 
6.12 
.25 
.69 
1.44 
4.76 
5.10 
11.96.. 
2,793 
36.17 
24.63 
28.07 
2.72 
.46 
1.25 
.68 
4.80 
1.22 
12.96.. 
3,612 
47.84 
37.65 
9.74 
2.99 
.30 
.17 
.75 
.17 
.39 
13.96.. 
2,508 
30.30 
47.53 
10.84 
1.60 
5.58 
.56 
.44 
2.99 
.16 
14.96.. 
3,803 
64.16 
19.99 
6.42 
3.10 
2.84 
2.52 
.26 
.71 
15.96.. 
1,563 
98.91 
.13 
.06 
.19 
.13 
.19 
.39 
16.96.. 
4,785 
62.90 
9.01 
18.06 
1.25 
2.01 
2.67 
1.33 
2.17 
.60 
17.96.. 
4,933 
41.60 
28.81 
19.62 
1.87 
2.59 
.57 
.89 
2.27 
1.78 
18.96.. 
5,646 
70.86 
.42 
15.02 
4.85 
.49 
.98 
4.83 
.78 
1.77 
19.96.. 
4,766 
46.37 
as.02 
6.73 
3.35 
2.35 
3.02 
3.86 
1.09 
.21 
20.96.. 
5,248 
59.18 
21.80 
6.25 
1.22 
2.04 
3.43 
4.08 
.69 
.91 
21.96.. 
3,772 
54.72 
26.73 
14.21 
1.06 
.95 
1.01 
.64 
.13 
.50 
22.96.. 
4,229 
45.40 
19.11 
23.22 
9.27 
2.46 
.11 
.31 
.07 
.05 
23.96.. 
4,736 
78.21 
7.43 
8.96 
4.39 
.46 
.25 
.13 
.13 
.04 
24.96.. 
1,527 
54.49 
16.76 
23.58 
4.19 
.26 
.20 
.13 
.26 
.13 
25.96.. 
746 
18.23 
7.51 
6.43 
15.55 
16.09 
23.59 
7.50 
3.76 
1.34 
26.96.. 
490 
in 0-20 
meter 
s. 
27.96.. 
762 
42. 
7.35 
9.98 
6.30 
4.20 
5.77 
6.29 
15.75 
2.36 
A glance at PI. VII will show that Diaptomus has a'strongly- 
marked minimum of occurrence in December and in January. 
There is an increase in February and March, but in both 1895 
and 1896, the number in May was very small. Diaptomus ap¬ 
pears to reach its maximum in the latter part of September and 
October. In the fall months, the collections consist mostly of 
mature forms. In the winter months most of them are immature. 
From the latter part of March to the latter part of May, nearly 
all are mature, and the females egg-bearing. In June there is a 
great preponderance of larvae. 
Apstein (’96, 179 and following) states that the maximum 
period of D. graciloides differs in different German lakes. The 
time of the maximum occurrence of Green Lake Diaptomi as re¬ 
corded above, does not agree with any of his observations. 
Birge (Birge’95 p. 448) states that the maximum time of Diapto¬ 
mus in Lake Mendota is in July. Inasmuch as Diaptomus is very 
little affected by differences of temperature, as will be shown 
later, I think these differences in maximum periods are prob- 
